WPF: Best way to raise a popup window that is modal to the page?

Question

I am building a WPF app using navigation style pages and not windows. I want to show a window inside a page, this window must be modal to the page, but allow the user to go to

Answer 1

Why not just use nested message pumps to create modal controls

http://www.deanchalk.com/wpf-modal-controls-via-dispatcherframe-nested-message-pumps/