I have one wall light in my small bathroom and I can pull a wire from the switch box to the attic above. (I want to add a can light) The problem is that is only a hot wire and my question is can I splice a nutral wire to another wire I have for a garage outlet in my attic. I can't get to the original light fixture box without cutting into my newly finished drywall ceiling and even then it could be tricky to fish down to the wall light box. 
