MDI App with Plugins

Hi
I want to write a mdi app where you basically can add new Document Templates (View and Doc) through a plugin. I found several similar examples on the net BUT in the examples they always create a new MainFrame (with new Menus and so on). What I want is the look (and behavior) of an regular MDI App (like menus change / toolbars...)
How can I do this in generall (or in detail)?

If you look at my article http://www.codeproject.com/library/piarchitecture.asp which covers an MFC plug-in architecture which allows additional doc templates etc. It also comes with some pre-designed plug-ins which you can use as well.