Here is another option, from exchangefaq.org.
Can I allow users to change their own mailbox info? Last update: December 08 1999 23:03
Yes. By default, only user accounts that have admin permissions on the Exchange directory can modify the items in the mailbox properties dialog. This is suboptimal for many sites, since staying on top of user changes can soak up a lot of time that can be better spent elsewhere.
The BORK includes a utility variously known as GALMOD, galmodify, and the Global Address List Modification tool. In short, it allows you to set up a web page that users can use to edit their own mailbox information. See the BORK for information on how to set it up and configure it.Better yet, see KB article Q242223.
Pretty much the same question you asked, except you just want one user to do it.