Enableing Auto lock Computer

dear all,

Is there any way to lock users computers after a period of time automatically from the server?
(I mean that I don’t want to go to each user and enableing screen saver with password to lock user computer, becuase in this way users can chnage the time or disbling autmatic lock.)

I am using windows 2000 server for server and windows 2000 profissional for users

thanks