add additional door trigger to oem alrm

I have a customer who is looking to add a pin switch to his tool box in a 2011 Ford F250 but wants to tie into his factory alarm, i have been looking at relays and door triggers to see if it will work and i think it will, but just seeing if anyone has done anything like this before, if i take a relay, 87 and 30 to ground 85 to - pulse trigger of the vehicle and 86 to the pin switch, that should do what i am looking to do and if the tool box lid is opened it should trigger the alarm......any thoughts?

Thanks

You will find that truck does not have normal pin switches for the doors. It has a normally closed door trigger system which rests at ground when the door is closed and breaks the ground when opened. Even the hood pin switch is this way, blue/orange @ BCM, brown 26 pin plug (F), pin 2. I would use this wire and use a relay to break this wire whenever the tool box is opened.