Thanks for the reply.
I don't think you can share a calendar on PST. In my case, shared
calendar is located in Mailbox of UserA.

I got the hack working but I was just wondering there must be a
simpler way to get the information like on whose calendar I am
creating the meeting. My scenario would be:
1. Open Outlook.
2. Open shared calendar of UserA (Suppose you have create and edit
permission on UserA's calendar).
3. Create a new meeting or modify an existing meeting.
4. Save the meeting.

At step 4, I need to find out that it is UserA's calendar and take
appropriate action. Is there a way to get this information using OOM
or MAPI?

Thanks,
Aditya