Silverlight Navigation - how to override Back button behavior -

I'm trying to override the default behavior of the browser's back button in Silverlight (v4). Each of my XAML pages has the ability to show options I want to hide these options when users will press the back button, or if the options are not visible, to go to the previous page. Whenever a user navigates to a page with a new query string, then set the Silverlight Frame back and set the forward digits. Is there another way of implementing my scenario besides implementing a query string element for my ShowOptions property?

BackupPress event in phone app page class

  backwardspress = = manpage_backpress ; Private Zero MainPage_BackKeyPress (Object Sender, CancelEventArgs e) {e.Cancel = true; // whatever you want}