Log off user workstation

I am running winnt 4.0 SP5 on the server and all workstations. At certain times of the day we must ask all users to log off the workstations using ctrl+alt+del then logoff. This is done to allow the application we are using on the workstations to update some data files from the server. I would like to be able to do this from a batch file at the server. The workstations are using TCP/IP and DHCP. When the network was first installed we were using SP 1 and had a batch file to shutdown or reboot the workstations from the server. With SP 5 those no longer work.

Thank you for any help you may be able to provide.