The OnClientReminderTriggering client-side event handler is called when an appointment reminder is about to be triggered,before the pop-up dialog is shown.
Two parameters are passed to the handler:
sender, the scheduler client object;
eventArgs, with three properties:
get_appointment() - the instance of the appointment.
get_reminder() - the reminder.
set_cancel() - used to cancel the event.
This event can be cancelled. Doing so effectively ignores the reminder.