Prism Navigation - ConfirmNavigationRequest - Subscribe to continuationCallback

I'm using Prism to navigate through my app.  My views are navigation aware and typically prompted with a dialog on IConfirmNavigationRequest.ConfirmNavigationRequest.  The contuationCallback action is executed based on the response.

I need to know when continuationCallback is executed whether true or false is passed to it.

var region; //prism region

EventHandler<RegionNavigationEventArgs> handler = null;
handler = (s, e) => {
  // do something
};

/* Navigating event is raised after continuationCallback(true). I 
need an event that is raised for true or false. */
region.NavigationService.Navigating += handler;

Thanks,

Daniel