I have a 2-gang switch box that houses two light switches. I'm replacing one of the switches with a Honeywell Programmable Light Switch PLS751, which requires both an ungrounded (hot) and a grounded (neutral) conductor.
To add this switch, I'm thinking I should route new 14/3 or 12/3 wiring to the box. I could alternatively route a single extra wire to the box also to act as the grounded (neutral). My question is: how the heck do I get either of these wires into the existing box? I've replaced a 1-gang box with a 2-gang before and routed new wire to that, but I'm clearly going to need some trickery to get a new run into an existing box without ripping it out first and fishing for it myself.