It isn't clear what you are trying to accomplish here. Are you trying to make it so:
Phone A-> Only goes out 66.x
Phone B-> Load balances between 66.x and 65.x
Either way, you will use route groups and route lists to accomplish this. Endpoints are load balanced within the route group, and the RGs are top-down in the RL.
You would have different CSSs applied to each of the phones. They would each have their own partititon, pointing to their own route lists that accomplish the call routing which you wish to have,
-Steve