RadControls for ASP.NET AJAX
The OccurenceDelete event occurs when a single occurrence is deleted,
but no exception is created in its place.
OccurenceDelete has two parameters:
sender is the scheduler control.
e is an object of type OccurrenceDeleteEventArgs.
It has the following properties
Appointment - the Master appointment;
OccurrenceAppointment - the Occurrence that is about to be deleted;
Cancel - if set to true, cancels the event;