Hi Chad,
At the moment, only the user can change their calendars. We have a PTO app that would possibly assist with this issue. The user would actually need to put in a PTO request and automatically update the calendars if approved.
Here is the link:
http://www.clarizen.com/appsmarketplace/item/pto_management.html
Also, what you described would be a feature request. You can post your idea in the "Share Your Ideas" section of our community forum.