I have an outlet that is located 24 inches from the bottom of wall but I need to move it down 12 inches. I don't think I can just add romex to it and move it, I remember something about putting in a box on the wall with a blank plate. I don't think it would be easy to locate the wire back to origin and replace entire wire with a longer one, but is there anything else I can do that is code compliant without having to put in a outlet accessible on the wall with a blank plate and hen the ac outlet below, I hope this makes sense.

Thanks,

mike