I'm condo owner; need access inside wall of another unit to replace a/c. Owner says access only on Sat. My contractor works weekdays. We're at impasse

I own a condo unit in New Britain, CT. The a/c system has failed and I have a contractor to put in a new system. He needs access inside the wall of a downstairs unit. (Note: I'll pay for restoration after our contractor is done and that's not an issue here.) The unit owner will allow access by our contractor only on Saturdays, and our contractor doesn't have Saturday hours because that's when his firm does emergencies. Our contractor is being great, and says he'll do the work evenings (after the unit owner gets home from work), and but the unit owner insists on the weekend. We're hoping that a letter from an attorney to the unit owner will make her more flexible. Note these condo units are in a very old converted building that has huge windows -- the rooms are 12-14 feet high, with lots of windows that are maybe 8 feet. Air conditioning in the summer is a necessity. (NOTE: I'D LIKE TO REMAIN ANONYMOUS FOR NOW JUST TO MAKE SURE THE ATTORNEY DOESN'T ALREADY DO WORK FOR THE CONDO ASSN)