This is a task for a programmer. I suggest using http://www.slipstick.com/outlook-developers/ or http://www.outlookcode.com (or hire one).

That said, to get by cheap, you might be able to use a notification tool like Watch Outlook Folders (http://www.SperrySoftware.com/Outloo...ok-Folders.asp). It will notify you (or anyone else) via email when an appointment has been added to a given calendar. Of course, that's all it does, it does not do approvals of any kind.