@Override
		public void handleEvent (Event event) {
			MenuItem [] menuItems = menu.getItems ();
			TreeItem [] treeItems = tree.getSelection ();
			for (int i=0; i<menuItems.length; i++) {
				String text = menuItems [i].getText ();
				int index = 0;
				while (index<treeItems.length) {
					if (treeItems [index].getText ().equals (text)) break;
					index++;
				}
				menuItems [i].setEnabled (index != treeItems.length);
			}
		}