Closing a window

Is there a way for Blitz to know when I've closed a window using the close-window 'X' in the corner? I'm using the debugger and keep accidentally closing the window with the X.

While Not MouseDown(1)
Print "Hello"
Wend
End

Errr, what?

There is a .dll or userlib for this kind of thing. Maybe a google search of the site might unearth it.

Found it:

http://www.blitzbasic.com/codearcs/codearcs.php?code=832

Thanks :)