Removing Software

I would like to remove our existing AntiVirus Software, and then install another product. My problem is we have WNT4 SP5 Workstation, users have no local ADMIN rights, and they cannot be granted ADMIN due to policies. I would like to find a way togrant a user ADMIN rights for the duration of their logon, while the logon script performs the uninstall of the previous software, and then installs the new software. We don’t have WSH installed on the clients. Has anyone had a similar problem andcome up with a solution?