Thank you for writing.
With the current implementation of RadCalendar
you can not use this approach. However as it seems very reasonable, we are going to allow you to update the template after the appointments have been loaded. The fix will become as part of our next internal build. I have updated your Telerik points for your cooperation.
Have a suggestion or face a problem - you can use the Ideas & Feedback portal
to submit ideas, feedback and vote for them.