How does Apple update the Airport menu while it is open? (How to change NSMenu when it is already open)

I've got a statusbar item that pops open an NSMenu, and I have a delegate set and it's hooked up correctly (-(void)menuNeedsUpdate:(NSMenu *)menu works fine). That said, that method is setup to be called before the menu is displayed, I need to listen for that and trigger an asynchronous request, later updating the menu while it is open, and I can't figure out how that's supposed to be done.

Thanks :)

EDIT

Ok, I'm now here:

When you click on the menu item (in the status bar), a selector is called that runs an NSTask. I use the notification center to listen for when that task is finished, and write:

[[NSRunLoop currentRunLoop] performSelector:@selector(updateTheMenu:) target:self argument:statusBarMenu order:0 modes:[NSArray arrayWithObject:NSEventTrackingRunLoopMode]];

and have:

- (void)updateTheMenu:(NSMenu*)menu {
    NSMenuItem *mitm = [[NSMenuItem alloc] init];
    [mitm setEnabled:NO];
    [mitm setTitle:@"Bananas"];
    [mitm setIndentationLevel:2];
    [menu insertItem:mitm atIndex:2];
    [mitm release];
}

This method is definitely called because if I click out of the menu and immediately back onto it, I get an updated menu with this information in it. The problem is that it's not updating -while the menu is open-.