I am glad to let you know that the new demo - Customizing the Appointment
, covers the functionality that you request. In the demo, we use a checkbox for the "Completed" status, but you can use the same approach and handle the Image button click server event to find the appointment object and then use UpdateAppointment of RadScheduler.
I suggest you review the code how we implement this and let me know if you have additional questions.
All the best,
the Telerik team
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