I'm very glad that it worked. Here is the situation of how this all functions: The left-most light switch in the stock 737 VC is hardwired to toggle a type-9 light. The XML code that I wrote, turns on a type-3 light whenever it detects that a type-9 light has been turned on, and turns it off the same way. The Nav light that is embedded in the Posky model is hardwired to be a type-3 light. You can not change the light type of the VC switch nor the light type of the Nav light in the model. Since we got the Nav light to go on with the switch in the VC we know the code is OK so we should not modify that.

However, I noticed in one of you previous posts that there were several type-3 lights defined in the [lights] section of your "aircraft.cfg" file that will also illuminate when the Nav lights are toggled. Namely:

light.4 = 3,  30.000,   0.000,  -3.000, Opensky_nacelle_refl ,   // front cargo
light.5 = 3, -33.000,   0.000,  -2.000, Opensky_nacelle_refl ,   // rear cargo
light.6 = 3,  40.000,   0.000,   4.000, Opensky_nacelle_refl ,   // pax door
light.16= 3, -62.000,   0.000,   7.000, Opensky_nav_yellow   ,   // Tail Nav Light

You can simply disable (comment out) any light that you don't want to have turned on by putting two slashes (such as: //) at the beginning of the line. My recommendation would be to comment out lights 4, 5, and 6, but leave light 16 because it is the rear Nav light.

Another thing you can do is assign lights 4, 5, and 6, to be type-4 lights that will turn on whenever the cockpit light goes on. Your Aircraft.cfg file would have entries like:

light.4 = 4 ...etc
light.5 = 4 ...etc
light.6 = 4 ...etc

Peter