+4  A: 

Not exactly, but you can do it. If you acquire a pointer to the File menu itself, you can give it a delegate object. One of the methods of the NSMenuDelegate protocol is (void)menuWillOpen:(NSMenu *)menu. You could probably use this to achieve the same effect as a target-action mechanism.

Dave DeLong
+1 for cleverness.
Abizern
More complicated than I had hoped for but I'm going to give it a shot.
Nick
I could not end up getting this to work and noticed the following note in the docs: "Special Considerations - Do not modify the structure of the menu or the menu items during this method."
Nick