Steering wheel control question

[txwayno]

I can't find any info on this here and didn't get any help on the other forum so in hoping someone here can tell me. My truck has an extra, not used (at least I don't think it does anything) button on the wheel like the one in this picture. Is it wired? Can I get to the wires under the dash to use it? I'd like to connect my train horn relay to it.
Thanks for any help.

 

[txwayno]

I know some of you know the wiring in these trucks inside and out. I would appreciate any help I can get with this. Looks like I'm gonna have to just start pulling wires and see what works.