I have a situation in which I have a receptacle under the kitchen sink that my dishwasher is plugged into. This receptacle is then operated by a switch on the backsplash on top of kitchen counter. We leave the switch in the on position so that we do not have to flip the switch each time we want to operate our dishwasher. I now want to install a garbage disposal and place a switch under the sink. I would like to come off of the receptacle described above. Could someone inform me how to connect to the receptacle so that the switch will operate but not interfere with leaving the switch on at the backsplash. Any assistance will be greatly appreciated.