Well im not checking or unchecking menu item. Im enabling and disabling, as in greying or ungreying a menu item that contains submenus. It works on menu items by them selves and submenus, but not menu items that contain submenus.
And I know it works, because like I said in the first post, it works great on menu items and submenu items, even without using GetSubMenu(). But it does not work on menu items with the (>) symbol that contain submenus. Its very strange as to why it doesn't. I'm not using a floating menu bar. More like a menu created from a resource.