responding to JInternalFrame events from JDesktopPane/JFrame

[Mike]

I have a main window (JFrame) that has a variable JDesktopPane. To the
JDesktopPane, I added a couple of JInternalFrame children. The problem
I'm having is that I don't know at the JFrame and JDesktopPane level
when the JInternalFrame window closes. When the JInternalFrame window
closes, I need to do certain things in the parent JFrame. However, I
don't want to pass a handle from JFrame to JInternalFrame. How can I
listen for JInternalFrame window closing events at the main window
(JFrame) level? Is there a creative way to do this?