It is still difficult for me to understand what you are trying to achieve. If your manager should be scrollable, it needs a fixed size on the visible screen.
Can you give more information about the behaviour of your user interface?
to calculate the height of your manager depending on the fields in it you can try this:
protected void sublayout(int maxWidth, int maxHeight)
int height = 0;
int fieldcount = getFieldCount();
for (int i=0; i < fieldcount; i++)
height += getField(i).getHeight();
setExtent(Width , height);