Hi selim,
You have several way to accomplish this:
1. You can create script task (unix script) to do this through defaults command to write needed values into corresponding plist files (to modify screensaver properties there is a com.apple.screensaver.plist)
After you are done - create Client task schedule task (you can see it on the image above) . Add task from step one and schedule Clietn task schedule to run on login or whatever you want.
Here you can find mac management scripts http://www.symantec.com/business/support/index?page=content&id=HOWTO51884 . But make sure to test these before you apply these scripts to managed clients.
2. If you are using software management solution, then you may try to setup mac management profiles.
You can find section in mac managmeent guid http://www.symantec.com/business/support/index?page=content&id=DOC6014 (page 94)
Thanks,
AndreiF