Excel add-in with modeless dialog
 

I have created an Excel add-in that uses a modeless dialog box. I want the
dialog box to be on top of Excel when Excel is the active window. If Excel
is minimized or is not the active window, I don't want my dialog to appear.
When I set the TopMost property of the dialog to True, the dialog remains on
top of every application. What can I do to get the desired behavior?
-- ckb