If specified, the OnClientAppointmentWebServiceUpdating client-side event handler is called when an appointment is about to be updated via Web Service call. In the case of server-side binding, the event will not be raised.
Two parameters are passed to the handler:
sender - the scheduler client object;
eventArgs with two properties:
get_appointment() - the appointment that is about to be updated.
set_cancel() - set to true cancel the operation.
This event can be cancelled.