There is no specific event that is fired when the time of a specific appointment has come. According to the provided information, indeed the reminders functionality in RadScheduler would be quite useful for your scenario. The following help article is quite useful on this topic:
If you don't want to display the reminder in the edit dialog, you can simply hide the reminder dropdown. For this purpose, it would be necessary to create a custom EditAppointmentDialog and set the Visibility of the radDropDownListReminder control to Hidden/Collapsed in the overridden OnLoad event. An alternative solution is to override the LoadReminders method and leave it empty without executing the basic logic.
I hope this information helps. If you need any further assistance please don't hesitate to contact me.
Dess | Tech Support Engineer, Sr.
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