Hello,
I don't think you'll be able to customize the menus (the only way I suppose this could be achieved would involve complicated event structures and/or calls to the windows API).
What I can suggest you is to simply disable those menus. You can see how to do it here:
http://forums.ni.com/ni/board/message?board.id=170&message.id=84319&requireLogin=False
Anybody has other ideas?
Regards,
JorgeM.