[Adrian]

menu_mc.onItemClick= function(node:XMLNode, level:Number){ 
    your_movie_clip.gotoAndStop(Number(node.attributes.frame));
 }

This is the code you should use. Replace your_movie_clip with the instance name of the movie clip you want to play. For example you could replace it with _root to play the main time line. Make sure your menu instance name is menu_mc.

This will work when you press either a menu item or a subitem. If you want to restrict it only to subitems, use the following:

menu_mc.onItemClick= function(node:XMLNode, level:Number){ 
    if(level == 2)
           your_movie_clip.gotoAndStop(Number(node.attributes.frame));
 }