There is an easier way to do this. For the owner of the mailbox, open outlook
(we will be using Outlook 2000)
In the file view, right click on Mailbox -mailbox name, properties,
on the permissions tab, give the new user whatever rights you want,reviewer is (read only for this level of the mailbox),
next select which folder the user needs say calender, right click properties->permissions tab, give the new user publishing editor (he can change all appointments,make new ones, delete)
exit out of outlook.
Wait for the replication interval (15minutes)
Goto the new users outlook,
Tools->Services->Microsoft Exchange Server->Properties->Advanced Tab, add mailbox, type in the mailbox you just changed permissions on, click okay. close out of the services tab. The mailbox should show up. The Calender should be the only folder he sees.
You can adjust permissions from there.
Hope this helps.
Otherwise,for what you have done already, open outlook for the new user, file->exit and logoff.
start outlook again, add the mailbox as stated above, and you should be able to see the mailbox.
Hope this helps.