[racket] Notification when window is closed

Hi,

Whenever the user clicks the 'Run' button in DrRacket,
all frames created by a previous run are closed.  Can we
be notified about that?

I tried augmenting on-close but it doesn't seem to be called
when the 'Run' button is clicked (although it is called when
the user clicks on the frame's close button).

Any suggestions?

Best regards,
Antonio.