That would require:
1) Exchange as your mail server
2) Ability to publish a custom form to the Organizational Forms library
3) A custom message (not appointment) form with code behind it to send it on to the right person, depending on the action taken. The sample code from my book (
http://www.outlookcode.com/member/book.aspx) contains a vacation request form in Chapter 20 with one level of approval that could get you started.
You could also potentially do something like that with Exchange workflow, if the Exchange administrator permits such applications to run on the server. See
http://msdn.microsoft.com/library/en-us/exchanchor/htms/msexchsvr_cdowf.asp
Another possibility would be InfoPath, if you are using the volume license version of Office 2003 Pro.
--
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers