Screen saver in workgroup manager

Hi I’m not sure if I’m posting this in the right section. I’m trying to push out a screen saver group policy throw the workgroup manger, what I’m trying to do is set a idle time for the screen saver. I have tried going to screen saver byhose and adding idle time but I get a error KEY IS NOT IN AN APPROPRIATE DOMAIN, has anyone got to to work? Is there another way to set a policy for the screen saver? Thanks