This post: blogs dot msdn dot com/oldnewthing/archive/2004/08/02/205624.aspx may provide some insight on how to accomplish this...
Hi,
coming back to your bug report (thanks for the link, I am an enthusiastic reader of "Old New Thing" myself

). Just wanted to keep you updated so you didn't think we forgot about the bug.
The problem is that the Floating TagTextBox is no dialog and does some ... yes, let's call them "hacks" to assure it does not get the focus by default unless you click into it. This is to prevent that if you close some other window of another application, the Floating TagTextBox would get the focus and the popup would appear. Unfortunately this involves chaning the WindowStyle of the window every time we get focus or receive focus. And that's where we still get problems with the shortcut. But we are working on it, we did not forget you.
Just wanted to keep you informed.
Best regards,
Martin