replying to Chris Lewis, Alexcwt wrote: I assume you want the undercabinet light to be independent of overhead light.
You can add a small 120v (coil) SPDT relay to create an always hot wire. It would draw a small amount of power when it's in the close position but save you the need to run another wire in the wall to the switch.
The con: it's going to make a click sound every time either of the 3 way switch is flicked.
Please check your local code before doing this.