What do you mean? Where you get your menu text and menu ID does not matter: CMenu allows you to add arbitrary text and numbers. You may as well load it from registry entries. If you want to change a menu from a menu bar, you would need to handle WM_INITMENU or override CWnd::OnInitMenu. There you can modify the menu - to the point of assembling a completely different menu.
"We trained hard, but it seemed that every time we were beginning to form up into teams we would be reorganised. I was to learn later in life that we tend to meet any new situation by reorganising: and a wonderful method it can be for creating the illusion of progress, while producing confusion, inefficiency and demoralisation." -- Caius Petronius, Roman Consul, 66 A.D.