Build nine foot ceiling area inside a pole barn with 12' walls

[breauxlg]

I'm trying to figure out an easy way to build a living area inside of a pole barn. I want that area to have 9 foot ceiling heights, but I'm framing in between the poles with my framed wall flush with the 6X6 poles on the inside of the exterior wall. If I change the ceiling height in a room bound by the exterior wall, it changes the exterior wall height, which needs to stay at 12 feet. 

Thanks in advance for any help.