How to signal that it's a modal dialog?

I'm using InstallPopup to create a modal dialog.  This is working fine.
However I need a way to indicate to the operator that this is a modal
dialog.  For example, in the CVI environment, if you select "Save Project As...", a FileSelect type
popup appears, but if you attempt to click on another window the FileSelect popup will blink
it's frame and beep.  I need to implement something like this for my popup's.
Any Ideas?

Thanks!

Angie