How can you update an NSMenu while it is active (visible)?

I have an NSMenu instance, 开发者_StackOverflowthrough which all communication with the Cocoa app will take place. If the menu is open, the background doesn't run, so how can I force an update while the menu is still active?

See Force NSMenu (nested submenu) update for Main Menu of Cocoa App and run that method in the background. (Don't forget to create an NSAutoreleasePool.)