Do you have your own office? Have you tried covering the vent? In one office I worked in I was able to cover the vent in the ceiling with a trash bag and duct tape. In the current office I'm in, I have magazines/junk mail placed over the vent (vent is in the floor).
hope this helps. always keep a sweatshirt or sweater on hand.
(one job, I even put a lap quilt on my legs when I sat at my desk because I was so cold. and wore gloves with the fingertips cut out.)
Rose Hall