Applying Group Policy Correctly

This is planned information just want to check if it will work before I do it.
Directory information:

CompanyWeb.Local (Domain) W2k3ent

 -->Workstations (OU)
       -->Mobile (OU)
       -->Remote (OU)
       -->Special (OU)

Ok, My Question, I have several WinXP(SP2) Clients that are placed between these 4 OU's. Now each of these OU's have different Group Policies applied to them. I have the policy to regulate similar settings applied to (excuse the NDS terminiology just stopped working for a company that used that and now with one that uses 2k3 and AD) Workstations.Companyweb.local. Now where I am not sure how this will work comes with the OU .Special.Workstations.CompanyWeb.local where as the policy in the Workstations has require CTRL-ALT-DEL to logon as enabled Clients in the Special (OU) need to have that as disabled. Now what I need to make sure is that All settings from the first Policy will be passed into Workstations in .special. but that the few settings in .special. Policy will override the settings of the first.

 My solution on how to do this is to just check the No Override in the Policy options but I wanted to make sure that it is only going to block ones that are explicity different and not block all settings from the Parent.