How to redrawing items in a form?

[nadia]

Hi,
I've a form which contains items.
when i chaged a list in this form at runtime some items should appear and some shouldn't,My problem is to get ride of the space between items i redrawing the items and this operation takes time.
Is there any way to do this whith out redrawing the items.
I've oracle 10g relase2 and forms 6i

Regards