I have a custom Appointment dialog because the one I use is very different from the default. I'm interrupting the default dialog by using e.cancel in RadScheduler1_AppointmentEditDialogShowing, and then displaying my custom form. This works great for new appointments but I need it to populate existing appointments when they are selected in the calendar. How can I retrieve the SQL ID of the appointment being selected? I need to pass this value to my custom form.