Update/Scan without logon

So, I've got a Mac running 10.5.6 and SAV 10.2. It's sitting on the network, but most of the time it won't have someone logged on to it. Is there any way to tie the scheduler to a system process so that it would get updates/scan while the computer is sitting at a logon screen? Or even so that it would automatically do it when someone logs on, rather than just at the specific times.

 

Any help would be much appreciated.