Vacation Request Calander in Outlook Public Folder how to do?

I would like to use Exchange/Outlook for create 2 folders, one called Vacation Requests, the other call Vacation Calendar.

My idea being users submit/add events to the Vacation Requests calander, the manager gets notified, approve/disapprove.

But how can I automate the approval being posted to the Vacation Calendar??

Thanks for any insights