using the App: variable scrollbar help and problems

It is a large amount of code, but please bare with me please.  I would really appreciate the help!

If I write a financial application where the user enters the initial investment, the compound interest rate period and duration of investment and it calculates the value.  Here is my code: each "screen" that appears on the emulator is its own class:

package com.rim.samples.Finance;

import net.rim.device.api.ui.UiApplication;

public class FinanceApplication extends UiApplication
{
    //VARIABLES FOR THE INVESTMENT GROWTH
    public double initialInvestment;
    public double interest;
    public int compoundPeriod;
    public int investmentLength;

    public static void main(String[] args)
    {
        FinanceApplication firstApplication  = new FinanceApplication();
        firstApplication.enterEventDispatcher();
    }

    public FinanceApplication()
    {
        //OPENING SCREEN FOR INVESTMENT GROWTH
        pushScreen(new Screen1());
    }

}

//SCREEN 1 INPUTS *INITIAL INVESTMENT*

package com.rim.samples.Finance;

import net.rim.device.api.ui.Color;
import net.rim.device.api.ui.DrawStyle;
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
import net.rim.device.api.ui.Font;
import net.rim.device.api.ui.Manager;
import net.rim.device.api.ui.MenuItem;
import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.XYEdges;
import net.rim.device.api.ui.component.BasicEditField;
import net.rim.device.api.ui.component.ButtonField;
import net.rim.device.api.ui.component.Dialog;
import net.rim.device.api.ui.component.LabelField;
import net.rim.device.api.ui.component.Menu;
import net.rim.device.api.ui.component.SeparatorField;
import net.rim.device.api.ui.container.HorizontalFieldManager;
import net.rim.device.api.ui.container.MainScreen;
import net.rim.device.api.ui.container.VerticalFieldManager;
import net.rim.device.api.ui.decor.Border;
import net.rim.device.api.ui.decor.BorderFactory;

public class Screen1 extends MainScreen implements FieldChangeListener
{

    //DECLARE MENU BUTTONS
    protected void makeMenu(Menu menu, int instance)
    {

        menu.add(_close);
    }
    private MenuItem _close = new MenuItem("Close", 110, 10)
    {
        public void run()
        {
            onClose();
        }
    };
    public boolean onClose()
    {
        Dialog.alert("Goodbye!");
        System.exit(0);
        return true;
    }

    //SCREEN 1 METHOD
    Screen1()
    {

        HorizontalFieldManager _fieldManagerTop = new HorizontalFieldManager(Manager.VERTICAL_SCROLL | Manager.VERTICAL_SCROLLBAR);
        VerticalFieldManager _fieldManagerMiddle = new VerticalFieldManager(Manager.VERTICAL_SCROLL | Manager.VERTICAL_SCROLLBAR);
        HorizontalFieldManager _fieldManagerBottom = new HorizontalFieldManager(Manager.VERTICAL_SCROLL | Manager.VERTICAL_SCROLLBAR);
        HorizontalFieldManager _fieldManagerButton = new HorizontalFieldManager(Manager.VERTICAL_SCROLL | Manager.VERTICAL_SCROLLBAR);

        //SET TITLE: FINANCIAL APPLICATION
        LabelField title = new LabelField ("Financial Application", LabelField.USE_ALL_WIDTH | DrawStyle.HCENTER);
        Font titleFont = this.getFont().derive(Font.BOLD | Font.ITALIC);
        title.setFont(titleFont);
        setTitle(title);

        //SET PAGE & INFO TEXT
        LabelField _page = new LabelField("Homepage ~ Initial Investment", LabelField.USE_ALL_WIDTH | DrawStyle.HCENTER);
        LabelField _info = new LabelField("\nThis application acts as a an investment or growth calculator.  The user inputs the amount of money he or she would like to invest originally, input the interest, the compound period, the regular monthly deposit into the investment, and the time her or she will have the investment and this application will calculate how much the investment will be worth.\n\n Please enter initial amount of money you are depositing into the investment.\n$XX.xx", LabelField.USE_ALL_WIDTH);

        //INPUT FIELDS TESTING!!!!

        //INPUT FIELD W/ BORDER
        BasicEditField _input = new BasicEditField();

        XYEdges padding = new XYEdges(10, 10, 10, 10);
        int color = Color.DARKGREEN;
        int lineStyle = Border.STYLE_SOLID;
        Border inputBorder = BorderFactory.createRoundedBorder(padding, color, lineStyle);
        _input.setBorder(inputBorder);

        //ADD FIELDS AND SEPARATORS
        add(_fieldManagerTop);
        add(new SeparatorField());
        add(_fieldManagerMiddle);
        add(new SeparatorField());
        add(_fieldManagerBottom);
        add(new SeparatorField());
        add(_fieldManagerButton);

        //ADD PAGE, INFO, INPUT
        _fieldManagerTop.add(_page);
        _fieldManagerMiddle.add(_info);
        _fieldManagerBottom.add(_input);

        //CREATE BUTTON TO NEXT PAGE
        ButtonField pressButton = new ButtonField("NEXT");
        pressButton.setChangeListener(this);
        _fieldManagerButton.add(pressButton);

    }

    //BUTTON FIELD CHANGE: ACTIONS
    public void fieldChanged(Field field, int context)
    {
        // PROBLEM IS HERE, I WANT WHATEVER IS TYPED INTO _input TO BE SET AS THE VARIABLE initialInvestmentFinanceApplication.initialInvestment=_input;

        UiApplication.getUiApplication().popScreen(this);
        UiApplication.getUiApplication().pushScreen(new Screen2());

    }

}

//SCREEN 2 INPUTS *INTEREST*

package com.rim.samples.Finance;

import net.rim.device.api.ui.Color;
import net.rim.device.api.ui.DrawStyle;
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
import net.rim.device.api.ui.Font;
import net.rim.device.api.ui.MenuItem;
import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.XYEdges;
import net.rim.device.api.ui.component.BasicEditField;
import net.rim.device.api.ui.component.ButtonField;
import net.rim.device.api.ui.component.Dialog;
import net.rim.device.api.ui.component.LabelField;
import net.rim.device.api.ui.component.Menu;
import net.rim.device.api.ui.component.SeparatorField;
import net.rim.device.api.ui.container.HorizontalFieldManager;
import net.rim.device.api.ui.container.MainScreen;
import net.rim.device.api.ui.container.VerticalFieldManager;
import net.rim.device.api.ui.decor.Border;
import net.rim.device.api.ui.decor.BorderFactory;

public class Screen2 extends MainScreen implements FieldChangeListener
{
    //DECLARE MENU BUTTONS
    protected void makeMenu(Menu menu, int instance)
    {
        menu.add(_home);
        menu.add(_close);
    }

    private MenuItem _home = new MenuItem("Home Page", 110, 10)
    {
            public void run()
            {
                onHome();
            }
    };

    public boolean onHome()
    {
        Dialog.alert("Homepage Selected");
        UiApplication.getUiApplication().popScreen(this);
        UiApplication.getUiApplication().pushScreen(new Screen1());
        return true;
    }

    private MenuItem _close = new MenuItem("Close", 110, 10)
    {
        public void run()
        {
            onClose();
        }
    };

    public boolean onClose()
    {
        Dialog.alert("Goodbye!");
        System.exit(0);
        return true;
    }

    //SCREEN 2 METHOD
    Screen2()
    {
        HorizontalFieldManager _fieldManagerTop = new HorizontalFieldManager();
        VerticalFieldManager _fieldManagerMiddle = new VerticalFieldManager();
        HorizontalFieldManager _fieldManagerBottom = new HorizontalFieldManager();
        HorizontalFieldManager _fieldManagerButton = new HorizontalFieldManager();

        //SET TITLE: FINANCIAL APPLICATION
        LabelField title = new LabelField ("Financial Application", LabelField.USE_ALL_WIDTH | DrawStyle.HCENTER);
        Font titleFont = this.getFont().derive(Font.BOLD | Font.ITALIC);
        title.setFont(titleFont);
        setTitle(title);

        //SET PAGE & INFO TEXT
        LabelField _page = new LabelField("Page Two ~ Interest", LabelField.USE_ALL_WIDTH | DrawStyle.HCENTER);
        LabelField _info = new LabelField("\nNow please enter the interest that will be put on this investment", LabelField.USE_ALL_WIDTH);

        //INPUT FIELD W/ BORDER
        BasicEditField _input = new BasicEditField();
        XYEdges padding = new XYEdges(10, 10, 10, 10);
        int color = Color.DARKGREEN;
        int lineStyle = Border.STYLE_SOLID;
        Border inputBorder = BorderFactory.createRoundedBorder(padding, color, lineStyle);
        _input.setBorder(inputBorder);

        //ADD FIELDS AND SEPARATORS
        add(_fieldManagerTop);
        add(new SeparatorField());
        add(_fieldManagerMiddle);
        add(new SeparatorField());
        add(_fieldManagerBottom);
        add(new SeparatorField());
        add(_fieldManagerButton);

        //ADD PAGE, INFO, INPUT
        _fieldManagerTop.add(_page);
        _fieldManagerMiddle.add(_info);
        _fieldManagerBottom.add(_input);

        //CREATE BUTTON TO NEXT PAGE
        ButtonField pressButton = new ButtonField("NEXT");
        pressButton.setChangeListener(this);
        _fieldManagerButton.add(pressButton);

    }

    //BUTTON FIELD CHANGE: ACTIONS
    public void fieldChanged(Field field, int context)
    {
        UiApplication.getUiApplication().popScreen(this);
        UiApplication.getUiApplication().pushScreen(new Screen3());
    }
}

//SCREEN 3 INPUTS *COMPOUND PERIOD*

package com.rim.samples.Finance;

import net.rim.device.api.ui.Color;
import net.rim.device.api.ui.DrawStyle;
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
import net.rim.device.api.ui.Font;
import net.rim.device.api.ui.MenuItem;
import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.XYEdges;
import net.rim.device.api.ui.component.BasicEditField;
import net.rim.device.api.ui.component.ButtonField;
import net.rim.device.api.ui.component.Dialog;
import net.rim.device.api.ui.component.LabelField;
import net.rim.device.api.ui.component.Menu;
import net.rim.device.api.ui.component.ObjectChoiceField;
import net.rim.device.api.ui.component.SeparatorField;
import net.rim.device.api.ui.container.HorizontalFieldManager;
import net.rim.device.api.ui.container.MainScreen;
import net.rim.device.api.ui.container.VerticalFieldManager;
import net.rim.device.api.ui.decor.Border;
import net.rim.device.api.ui.decor.BorderFactory;

public class Screen3 extends MainScreen implements FieldChangeListener
{
    //DECLARE MENU BUTTONS
    protected void makeMenu(Menu menu, int instance)
    {
        menu.add(_home);
        menu.add(_close);
    }

    private MenuItem _home = new MenuItem("Home Page", 110, 10)
    {
            public void run()
            {
                onHome();
            }
    };

    public boolean onHome()
    {
        Dialog.alert("Homepage Selected");
        UiApplication.getUiApplication().popScreen(this);
        UiApplication.getUiApplication().pushScreen(new Screen1());
        return true;
    }

    private MenuItem _close = new MenuItem("Close", 110, 10)
    {
        public void run()
        {
            onClose();
        }
    };

    public boolean onClose()
    {
        Dialog.alert("Goodbye!");
        System.exit(0);
        return true;
    }

    //SCREEN 3 METHOD
    Screen3()
    {

        HorizontalFieldManager _fieldManagerTop = new HorizontalFieldManager();
        VerticalFieldManager _fieldManagerMiddle = new VerticalFieldManager();
        HorizontalFieldManager _fieldManagerBottom = new HorizontalFieldManager();
        HorizontalFieldManager _fieldManagerButton = new HorizontalFieldManager();

        //SET TITLE: FINANCIAL APPLICATION
        LabelField title = new LabelField ("Financial Application", LabelField.USE_ALL_WIDTH | DrawStyle.HCENTER);
        Font titleFont = this.getFont().derive(Font.BOLD | Font.ITALIC);
        title.setFont(titleFont);
        setTitle(title);

        //SET PAGE & INFO TEXT
        LabelField _page = new LabelField("Page Three ~ Compound Period", LabelField.USE_ALL_WIDTH | DrawStyle.HCENTER);;
        LabelField _info = new LabelField("\nNow please enter the compound period.\npress spacebar to go through the choices:", LabelField.USE_ALL_WIDTH);;

        //ADD FIELDS AND SEPARATORS
        add(_fieldManagerTop);
        add(new SeparatorField());
        add(_fieldManagerMiddle);
        add(new SeparatorField());
        add(_fieldManagerBottom);
        add(new SeparatorField());
        add(_fieldManagerButton);

        //OBJECT CHOICE FIELD
        String choicestrs[] = {"Weekly", "Bi-Weekly", "Monthly", "Quarterly", "Annually"};
        ObjectChoiceField choice = new ObjectChoiceField("Compound Period: ", choicestrs, 0);

        //ADD PAGE, INFO, OBJECT CHOIE TO FIELD
        _fieldManagerTop.add(_page);
        _fieldManagerMiddle.add(_info);
        _fieldManagerBottom.add(choice);

        //CREATE BUTTON TO NEXT PAGE
        ButtonField press2Button = new ButtonField("NEXT");
        press2Button.setChangeListener(this);
        _fieldManagerButton.add(press2Button);

    }

    //BUTTON FIELD CHANGE: ACTIONS
    public void fieldChanged(Field field, int context)
    {
        UiApplication.getUiApplication().popScreen(this);
        UiApplication.getUiApplication().pushScreen(new Screen4());
    }
}

//SCREEN 4 INPUTS *LENGTH OF INVESTMENT*

package com.rim.samples.Finance;

import net.rim.device.api.ui.Color;
import net.rim.device.api.ui.DrawStyle;
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
import net.rim.device.api.ui.Font;
import net.rim.device.api.ui.MenuItem;
import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.XYEdges;
import net.rim.device.api.ui.component.BasicEditField;
import net.rim.device.api.ui.component.ButtonField;
import net.rim.device.api.ui.component.Dialog;
import net.rim.device.api.ui.component.LabelField;
import net.rim.device.api.ui.component.Menu;
import net.rim.device.api.ui.component.SeparatorField;
import net.rim.device.api.ui.container.HorizontalFieldManager;
import net.rim.device.api.ui.container.MainScreen;
import net.rim.device.api.ui.container.VerticalFieldManager;
import net.rim.device.api.ui.decor.Border;
import net.rim.device.api.ui.decor.BorderFactory;

public class Screen4 extends MainScreen implements FieldChangeListener
{
    //DECLARE MENU BUTTONS
    protected void makeMenu(Menu menu, int instance)
    {
        menu.add(_home);
        menu.add(_close);
    }

    private MenuItem _home = new MenuItem("Home Page", 110, 10)
    {
            public void run()
            {
                onHome();
            }
    };

    public boolean onHome()
    {
        Dialog.alert("Homepage Selected");
        UiApplication.getUiApplication().popScreen(this);
        UiApplication.getUiApplication().pushScreen(new Screen1());
        return true;
    }

    private MenuItem _close = new MenuItem("Close", 110, 10)
    {
        public void run()
        {
            onClose();
        }
    };

    public boolean onClose()
    {
        Dialog.alert("Goodbye!");
        System.exit(0);
        return true;
    }

    //SCREEN 4 METHOD
    Screen4()
    {
        HorizontalFieldManager _fieldManagerTop = new HorizontalFieldManager();
        VerticalFieldManager _fieldManagerMiddle = new VerticalFieldManager();
        HorizontalFieldManager _fieldManagerBottom = new HorizontalFieldManager();
        HorizontalFieldManager _fieldManagerButton = new HorizontalFieldManager();

        //SET TITLE: FINANCIAL APPLICATION
        LabelField title = new LabelField ("Financial Application", LabelField.USE_ALL_WIDTH | DrawStyle.HCENTER);
        Font titleFont = this.getFont().derive(Font.BOLD | Font.ITALIC);
        title.setFont(titleFont);
        setTitle(title);

        //SET PAGE & INFO TEXT
        LabelField _page = new LabelField("Page Four ~ Investment Length", LabelField.USE_ALL_WIDTH | DrawStyle.HCENTER);
        LabelField _info = new LabelField("\nNow please enter how long you will have this investment for?\nPlease enter the amount in months:", LabelField.USE_ALL_WIDTH);

        //INPUT FIELD W/ BORDER
        BasicEditField _input = new BasicEditField();
        XYEdges padding = new XYEdges(10, 10, 10, 10);
        int color = Color.DARKGREEN;
        int lineStyle = Border.STYLE_SOLID;
        Border inputBorder = BorderFactory.createRoundedBorder(padding, color, lineStyle);
        _input.setBorder(inputBorder);

        //ADD FIELDS AND SEPARATORS
        add(_fieldManagerTop);
        add(new SeparatorField());
        add(_fieldManagerMiddle);
        add(new SeparatorField());
        add(_fieldManagerBottom);
        add(new SeparatorField());
        add(_fieldManagerButton);

        //ADD PAGE, INFO, INPUT
        _fieldManagerTop.add(_page);
        _fieldManagerMiddle.add(_info);
        _fieldManagerBottom.add(_input);

        //CREATE BUTTON TO NEXT PAGE
        ButtonField pressButton = new ButtonField("NEXT");
        pressButton.setChangeListener(this);
        _fieldManagerButton.add(pressButton);

    }

    //BUTTON FIELD CHANGE: ACTIONS
    public void fieldChanged(Field field, int context)
    {
        UiApplication.getUiApplication().popScreen(this);
        UiApplication.getUiApplication().pushScreen(new InvestmentWorth());
    }
}

//INVESTMENT WORTH

package com.rim.samples.Finance;

import net.rim.device.api.ui.Color;
import net.rim.device.api.ui.DrawStyle;
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
import net.rim.device.api.ui.Font;
import net.rim.device.api.ui.Manager;
import net.rim.device.api.ui.MenuItem;
import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.XYEdges;
import net.rim.device.api.ui.component.ButtonField;
import net.rim.device.api.ui.component.Dialog;
import net.rim.device.api.ui.component.LabelField;
import net.rim.device.api.ui.component.Menu;
import net.rim.device.api.ui.component.SeparatorField;
import net.rim.device.api.ui.container.HorizontalFieldManager;
import net.rim.device.api.ui.container.MainScreen;
import net.rim.device.api.ui.container.VerticalFieldManager;
import net.rim.device.api.ui.decor.Border;
import net.rim.device.api.ui.decor.BorderFactory;

public class InvestmentWorth extends MainScreen
{

    //DECLARE MENU BUTTONS
    protected void makeMenu(Menu menu, int instance)
    {

        menu.add(_close);
    }
    private MenuItem _close = new MenuItem("Close", 110, 10)
    {
        public void run()
        {
            onClose();
        }
    };
    public boolean onClose()
    {
        Dialog.alert("Goodbye!");
        System.exit(0);
        return true;
    }

    //SCREEN 1 METHOD
    InvestmentWorth()
    {

        HorizontalFieldManager _fieldManagerTop = new HorizontalFieldManager(Manager.VERTICAL_SCROLL | Manager.VERTICAL_SCROLLBAR);
        VerticalFieldManager _fieldManagerMiddle = new VerticalFieldManager(Manager.VERTICAL_SCROLL | Manager.VERTICAL_SCROLLBAR);
        HorizontalFieldManager _fieldManagerBottom = new HorizontalFieldManager(Manager.VERTICAL_SCROLL | Manager.VERTICAL_SCROLLBAR);

        //SET TITLE: FINANCIAL APPLICATION
        LabelField title = new LabelField ("Financial Application", LabelField.USE_ALL_WIDTH | DrawStyle.HCENTER);
        Font titleFont = this.getFont().derive(Font.BOLD | Font.ITALIC);
        title.setFont(titleFont);
        setTitle(title);

        //SET PAGE & INFO TEXT
        LabelField _page = new LabelField("Homepage ~ Initial Investment", LabelField.USE_ALL_WIDTH | DrawStyle.HCENTER);
        LabelField _info = new LabelField("\nHere is the worth of your investment:\n", LabelField.USE_ALL_WIDTH);

        //INPUT FIELD W/ BORDER
        LabelField _worth = new LabelField();
        XYEdges padding = new XYEdges(10, 10, 10, 10);
        int color = Color.BLACK;
        int lineStyle = Border.STYLE_SOLID;
        Border inputBorder = BorderFactory.createRoundedBorder(padding, color, lineStyle);
        _worth.setBorder(inputBorder);

        //ADD FIELDS AND SEPARATORS
        add(_fieldManagerTop);
        add(new SeparatorField());
        add(_fieldManagerMiddle);
        add(new SeparatorField());
        add(_fieldManagerBottom);

        //ADD PAGE, INFO, INPUT
        _fieldManagerTop.add(_page);
        _fieldManagerMiddle.add(_info);
        _fieldManagerBottom.add(_worth);

    }

}

So when I run on the emulator, on Blackbery 8520 SDK emulator, it doesn't let me scroll upwards on the first screen to see the rest of the text, it's like the cursor on the button sticks or editing field base so it wont allow to exceed upwards the button or basic edit field , but I can scroll between them.

Second problem is trying to address (as defined in the first class) variables to different edit fields so when something is typed in (double), it is placed in the variable to use in the rest of the program.  I want to make sure the basic edit fields only allow "double" number entered, otherwise it displays a message 'incorrect type '.   Please help me with this, or give me some advice.

I would REALLY appreciate it.