Hello Kenneth Elman,
We do not have a built in behavior of RadScheduler which can show any unavailable appointments. We should definitely think about this feature though. At the moment we only have a work time period which you can define using the Start and End properties. Here is a sample code how to access the WorkTime in RadScheduler DayView -
I hope this helps. Do not hesitate to write me back if you have further questions.
All the best,
the Telerik team