Question : DNS registration not updated for computer as it moves between IP networks

I have users with notebook computers running Vista who obtain DHCP addresses from a Microsoft Windows 2003 DHCP server when in the main office.  When the same users work from a remote office, they get addresses on a different IP network served from a pool on a Cisco router, and when they work from the road over an SSL VPN they get addresses from a third address pool served from a Cisco router.  The users frequently obtain new addresses from each of these services in the same day.  This results in multiple entries in the AD integrated DNS server for each notebook.  I'm looking for a way to get only a single entry in the DNS server for each computer and have it updated dynamically each time the client address changes.  I have tinkered with the aging and scavenging features of DNS without success.

Answer : DNS registration not updated for computer as it moves between IP networks

I think we should go ahead and close this question since it has been open for so long with little activity and the solution has not been found.  Thanks to those who took the time to get involved.