2 horns through stock button

Ok, I'm hoping someone can help me out here. I'm going to be wiring up a 2nd horn. I want to switch between which horn is being heard. I want to use a normal on/off toggle as I want to use the steering wheel to control the horn still. How would I be able to wire up a relay to get this to work? Hopefully thats easy to understand.

What kind of horn are you going to use for your second horn? The way you do it is find the horn trigger wire in the ignition harness and cut it. You then take a relay and wire as follows. pin 86 to an ignition 12v pin 85 to toggle switch pin 87 to second horn trigger* pin 87a to oem wire that was cut to horn side pin 30 to the oem wire that was cut towards steering wheel side second pin on toggle switch to ground *depending on vehicle it will be dependent upon the oem trigger. Usually negative(-) but on some vehicles like VW it is positive(+) That circuit will let you choose horn when vehicle is running that way you don't leave the relay on and drain your battery.The wire I'm test'n isn't doin' what it's supposed to be doin'... I am so glad I printed that tech sheet, with the wrong info.

Do it right the first time... or I might have to fix it for ya