Menu problem

I have a really simple rollover menu that has rollover submenus. I’m just using an invisible button around the menu and submenu to make it disappear. This works fine apart from when you are on a submenu and you rollback over the main menus other buttons, the submenu does not disappear. Is there a bit of actionscript I can apply to the main menu button to make sure all other submenus are shut down first? I’ve tried using
on (rollover) {(button3_mc._enabled = false; ) on the other buttons but this doesn’t seem to work. can anyone help?