Hello Lee,
I would suggest you to refer to our online demo below, which demonstrates how to create an appointment in the RadScheduler, when dragging and dropping elements from an external control. The suggested approach in the demo, demonstrates how to achieve this using the client-side API of the RadScheduler and the external control, which would be helpful for the scenario that you attempt to achieve.
http://demos.telerik.com/aspnet-ajax/scheduler/examples/creatingappointmentswithdraganddrop/defaultcs.aspx
Regards,
Nencho
Telerik
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