Group Policy cumulative effect testing

I am looking for the best way to test or calculate the cumulative effect of overlapping policies. I am about to setup group policies on a network that is mostly (about 2/3) win98 systems. The desire is to lock down all of the users, with an occasional exception on specific XP based systems on the network. What I would like to do, but do not know how is to set a user policy to lock them down, but have a machine policy that will override the user policy and let the restrictions be lifted when needed, but only on certain machines, not on the user for just any machine. Can anyone offer me some guidance or recommend a location where I can find some guidance on this?