many dynamic forms

Question

hi everybody
I want to make something like icq - a messaging programm. The main part is almost done, but

there`s a problem.
Whrn I click a contact from a list there opens a dialog window, which I dynamically create

like Form form1=new Form() and then dynamically add buttons etc.
When I click again the same contact, the simiar window opens and so on.
How could I control that?
I mean where could I fint what dynamic forms are already open?
On the other hand, when I recieve a message from somebody, how should I find if the dialog

box with the sender is already open?