Calender

Hello
I am running exchange service 2003 with windows 2003. Recently i got a request from the user about sharing the calender.
We have a set up
1. Personnel folder-built with calender
2.Mailbox for the user-
i shared mailbox calender for particular user/but this caleder can view everyone in our company
Now my question is how to restrict this calender
Help me please.
suresh