switch with 2 outputs?

heres what im trying to achive
im doing a light and siren package on a car(before i get yelled out we have the authorization from the city)

i want to addd the horn cycle function on the siren which uses the horn to change siren tones
usually i just disconect the factory horn and and be done with it...
but this is going to be dual purpose
so i want to have the hron function normally then when the lights are activated have that + output activate a relay switching from the neg pulse on horn to a neg pulse to the siren itself. without honking the factory horn
thanks

i should of mentioned that factory horn a neg line,,,
does it matter?
sooo
it will keep factory horn working normal until lights are active then factory horn wont beep but it will still give me a neg pulse for the siren everytime horn button is pushed
thanks

The actual wire going to the horn itself is positive in nature.

The way I described it, there will be a positive pulse, you will have to use a second relay to get negative out. Give me a minute and I can modify the instructions for negative trigger and negative out.

oh ok because when i looked up the wire codes it says that the horn wire is negative , so i assumed it was a neg pulse ..i hope im making sense of what i want to do i dont want to confuse you
thanks

The low current section of the horn wire (Between the Horn button and the relay) is negative in nature. The wire from the relay to the actual horn is positive. The horn is grounded to the chassis, there is probably only one wire leading to it.