wondering if i can just come out of the N M sconce box in the wall with N M cable to add a light fixture in a 37 floor hotel. the building was built in 1980 Boston MA with romex through out the guest rooms, even the 277v electric heat is feed with romex. the rest of the building however is feed with BX or MC. all i want to do is add a light in the cieling. i can't imagine having to change out the N M box with a metal one and then use MC, it just seems silly to me that there is already thousands of feet of romex aleady. i can't seem to find it in the nec an exeption that fits my problem. please tell me what ya's think:?