List of Windows Owned by Second UI Thread

Hello:

I have two UI threads.  I can get a list of UI threads for the first (main) UI thread; however, I am unable to retrieve a list of windows owned by the second UI thread.  Is this possible?

For example, in the first UI thread, I can call Application.Current.Windows, but that is only returning a list of Windows owned by the first (main) UI thread.  I thought it would be ALL windows owned by ALL threads for the application, but it doesn't seem to be this way.

Is there some trick I could use with the Dispatcher to get the Windows?

Thank you, all, for your help.

Trecius