Custom Admingroups/tasks based on domain name

Hi, I'm pretty new to MDT but I'm trying to set different cs.ini settings based on the domain name I select in wizard. Is there an easy way to do this? 

For example, If I put in credentials and say join "OldDomain", I want:

Administrators001=OldDomain\Group1
Administrators002=OldDomain\Group2

but if I say "NewDomain" I want:

Administrators001=NewDomain\Group1
Administrators002=NewDomain\Group2

Also, once I get to the TaskSequence a few things would need to change as well, but I think I can probably handle that part.