In theory you can do this by iterating through your collection of appointments, check if there is a conflict, resolve the conflict by inserting the new appointment time and create two separate appointments (maybe name then Part1 and Part2) to make up the balance. There is no straight forward way to do this with a single line of code, but with a little creativity you could pull it off.
RadCalendar fires off many events (see the list here
) that you can use to your advantage. In your case you can use AppointmentCreating to do the iteration of the current appointment list. In the event handler you then do the work to rearrange the appointments to make the split.)
I hope this helps