[Samba] Samba + ldap pdc and SUS

[Mattia]

Hi all,
I'm here again ith a non-strictly samba related problem, but I hope 
someone in the list has already faced and perhaps solved it...
I've got a 60 clients network (most Windows 200 and XP) organized in a 
domain. The pdc and bdc run on Fedora 2 + samba 3.0.7-2.FC2 + 
openldap-2.1.29-1, and everything works fine.
To limit the use of internet bandwidth I installed a Windows 2003 server 
acting as SUS (Software Update Services) server (for those who don't 
know it... it's something similar to an internal Windows Update server)
The problem is I can't configure the clients to point to the new server 
instead of the official Windows Update servers. If the domain would have 
been Windows-based I would have done it with a group policy, but I have 
no possibility to do it with Samba.
I've tried to remotely modify the registry keys on the clients, but with 
no success (the change requires also a local policy change, not just a 
registry key change, and I don't know how to do it remotely).

Has anyone of you guys ever tried a setup like this?

Sorry if I'm a little bit OT...
Thanks!

Bye... Mattia