add a switch to an existing three core light circuit

[mur30]

hello,
I have added a porch to my house. I was hoping to extend an existing lighting cable, which was used for an outside light, to light the porch. The cable is coming from a switch inside the house. I was hoping to add a switch to control a light from within the porch and blank the existing switch.

[sparx]

And your question is???
Assuming your porch now brings the old outside light cable inside it, then you could connect the old sw. wires together in old sw. box with a connector & fit a blank plate where sw.was.
without knowing more it is hard to say how to run/extend wiring to light & new sw. position, but possibly could fit Joint box to end of existing cable and run to sw. position & to light position and join together as shown in projects' wiring a light'
regards SPARX

[mur30]

thanks sparx. I'll wire it as you suggest.