Dynamic List box problem

Hi,
I managed to fill a ListBox onClick with entries. Unfortunately the
ListBox expands before onClick is catched (before data is reloaded).
Therefore the user has to click a scond time after the entries are
loaded.

Is there a way to force a ListBox to NOT expand when clicking on it?
And is there also a way to force a ListBox to expand by code?

A native call of
$wnd.document.getElementById('listBoxId').click();
does not work.

Cheers,
M