Scrolling in ComboBox popup

[Jeffrey Barish <jeff_barish earthlink net>]

Is there a way to control scrolling in the popup for a ComboBox?  I have a
ComboBox with only 10 items.  The ComboBox pops up a window with the active
item positioned near the top.  If the active item is not one of the first
two items, then scrollbars appear and there is a vast empty space below the
last item.  I can scroll to the top, at which point the scrollbars
disappear and the items neatly fill the space that was originally
available.  I don't understand why the ComboBox is resorting to scrollbars
when the popup has enough room for all items.  Is there a way to tell the
ComboBox not to use scrollbars?  Can I force the first item to appear so
that the scrollbars disappear?
-- 
Jeffrey Barish