Blackberry - Custom size EditField

I am trying to put together a dialog that should look like this:

Fill in the below fields
_______________ likes ____________________

where the "_" lines are the EditFields.

I am sticking all the fields in a HorizontalFieldManager, which I add to the dialog. Unfortunately, the first EditField consumes all the space on the first line. I have tried to override the getPreferredWidth() method of the EditField by creating my own class extending BasicEditField, but have had no success.

Surely there must be a simple way to force a certain size for an edit field. What am I missing?

Just like DaveJohnston said:

class LikesHFManager extends HorizontalFieldManager {
    EditField mEditFieldLeft;
    LabelField mLabelField;
    EditField mEditFieldRight;
    String STR_LIKES = "likes";
    int mLabelWidth = 0;
    int mEditWidth = 0;
    int mOffset = 4;

    public LikesHFManager() {
        mEditFieldLeft = new EditField();
        mLabelField = new LabelField(STR_LIKES);
        mEditFieldRight = new EditField();

        mLabelWidth = mLabelField.getFont().getAdvance(STR_LIKES);
        int screenWidth = Display.getWidth();
        mEditWidth = (screenWidth - mLabelWidth) >> 1;
        mEditWidth -= 2 * mOffset;

        // calculate max with of one character
        int chMaxWith = mEditFieldLeft.getFont().getAdvance("W");
        // calculate max count of characters in edit field
        int chMaxCnt = mEditWidth / chMaxWith;

        mEditFieldLeft.setMaxSize(chMaxCnt);
        mEditFieldRight.setMaxSize(chMaxCnt);

        add(mEditFieldLeft);
        add(mLabelField);
        add(mEditFieldRight);
    }

    protected void sublayout(int maxWidth, int maxHeight) {

        int x = 0;
        int y = 0;

        int editHeight = mEditFieldLeft.getPreferredHeight();
        int labelHeight = mLabelField.getPreferredHeight();

        setPositionChild(mEditFieldLeft, x, y);
        layoutChild(mEditFieldLeft, mEditWidth, editHeight);
        x += mEditWidth;
        x += mOffset;

        setPositionChild(mLabelField, x, y);
        layoutChild(mLabelField, mLabelWidth, labelHeight);
        x += mLabelWidth;
        x += mOffset;

        setPositionChild(mEditFieldRight, x, y);
        layoutChild(mEditFieldRight, mEditWidth, editHeight);
        x += mEditWidth;

        setExtent(x, Math.max(labelHeight, editHeight));
    }
}