Windows 8.1 phone : How do I get the Calender to call back my app

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C#5.0

I have successfully employed the Windows.ApplicationModel.Appointment class within my application in order to create/update and delete appointments in the phones calendar.

However I understand that by setting the Uri property of the Appointment class to that of my app's I can get the calender to inform my application of any editing actions it performs upon the data that my app sent it.

In my applications App.Manifest I have created a protocol named simply "pfmedmon" and I have tried setting the Appointment.Uri to "pfmedmon://" but have not been able to receive a callback from the calender app.

I am looking to catch this within my App.xaml.cs OnActivated event.

Any clues as to where I have gone wrong very gratefully received.

Thanks