I have a set of controls and logic that must be invoked from several pages 
within a web application as a popup dialog, so I intend to use a userControl 
contained in a panel extended with the modalPopupExtender to get this 
behavior.  I want to deal with showing and hiding the popup in server-side 
code, so I've set the TargetControlID to a hidden (style=display:none;) 
button and not set the OkButton or CancelButton.  The userControl has several 
events designed to signal the disposition of the user's interaction with the 
control.  The problem that I am having is that whenever an action is taken on 
the control that causes an interaction with the server side code, the popup 
is closed and my events are never fired in the containing page.  Has anyone 
successfully used the modalPopupExtender in this manner?