Putting in the new switch is easy enough, as is running the cable through the attic and down to the old box, but how do I get the cable into the the first steel box? Since I do not have access to the outside of the existing box, I cannot put a cable clamp on it. Do I just live without a cable clamp? Obviously I can not secure the cable to the wall, as required by code either. It seems to me that any work like this will be against code unless you rip the drywall off. Any help would be appreciated.