Unfortunately, the public APIs for the ribbon interface are broken to an extent. I havent checked recently, but as an add-on, it was impossible to get 2 excel

Unfortunately, the public APIs for the ribbon interface are broken to an extent. I havent checked recently, but as an add-on, it was impossible to get 2 excel windows to display different values in a textbox embedded in a ribbon for 2 sheets openned in the same excel process. Despite the appearance of being separate processes because of separate windows, excel is basically a detached MDI interface where each sheet gets its own window, but same process. I think the other Office products are the same (but I'm not sure). I dont know how many hours I wasted at a previous employer trying to figure out what was wrong, but finally gave up after many frustrating hours.