In a typical home, a bedroom is converted into a home office. The chances are that the air conditioning system was not designed to account for the added heat loads that are associated with home offices, such as computers, monitors, additional lighting, printers, copiers, scanners, TV's, etc. All of these items add a great deal of heat to your office. Since your system was not designed to account for these items, the room will always be hotter than the rest of the home. You can have an air balance done to slightly help this problem, but it will not wholly remedy it. The only solution that will completely fix the problem is to have duct modifications made and possibly a new unit installed.