Field Validation being inconsistent

Hi-

I created a field validation for the Service Request Type, but the changes aren't working.  I want to limit all users (except the following roles: Administrator, Specials, & Specials- Melodie) to not be ablet to create the US or OUS Specials Service Request.

This works to limit only those roles to be able to create US Specials SR:

UserValue('<Role>')='Administrator' or (UserValue('<Role>')<> 'Administrator' and [<Type>]<> 'US Special Request') or (UserValue('<Role>')='Specials' and [<Type>] = 'US Special Request') or (UserValue('<Role>')='Specials- Melodie' and [<Type>] = 'US Special Request')

This works to limit only those roles to be able to create OUS Specials SR: