Centralized Contact Management

Hello All,

I am looking for a centralized way to administer Contact
Lists in Windows Messenger. My company (20 people) uses it
for office communication. As we've grown, the distributed
method of administration has gotten unwieldly, having to
go to each workstation to delete someone.

Ideally, I'd like some sort of a management console where
I can add a user in one spot, and s/he appears in
everyone's contact list automatically.

Here's what I have to work with:
- All clients are Windows XP Pro
- Server running the network is Windows 2000 Server
- Exchange Server has been outsourced to USA.Net and is
offsite

I looked into Exchange IM, but USA.Net tells me that
adding a user via their Provisioning Console (read:
administration tool) will not give me what I want, which
is to have a new user automatically appear in all the
contact lists.

I'm open to just about any idea for centralized
administration. Is there a registry setting I can change?
Is there a file I can edit? A script I can run? An
integration I can do? Less preferably, a product I can buy?

Thanks in advance,
-James Damato