Horn wire access / steering column harness

[gpshslax]

I'm back to installing my keyless entry system in my gen. III sable (from my earlier post). I hooked up the locks last week and they work, I've just wired the relay for the trunk release and that works fine, and I've all but attached the parking light conformation (it got cold and dark so I left that for tomorrow).

I also wanted to try and wire the horn to honk when the lights flash. The horn has the reverse polarity of the parking lights so I should be able to attach the horn wire to the negative trigger wire for the lights I think (let me know if that sounds wrong to anyone). My main question is where the wire for the horn is accessable? My wireing chart says "at steering column harness" but I can't see any wires coming down from the steering column witht he correct color code (yellow/light green). Do I have to remove the cover from the steering column to make this work? I hope I don't have to remove the steering wheel as this look tricky in Chiltons (with the air bag and all) and if I have to do that then I'll probably forget about it. All suggestions welcome.

Thanks,
Matt Walters