Adding a door 3rd door pin

Hi, I have a 94 Civic hatch. When the alarm was installed the doors work fine but the backglass doesnt have a door pin like the front two. If I were to add one in the back and cut into the wires on the passenger side would the alarm sound if the backglass was open and the passenger side was closed?? A relay seems like it would fix this problem but I dont have any experience in this kind of stuff. From the diagrams I have seen it looks like the relay would only be able to power one or the other... so if someone out there could help me, you could help save a car. :) Thanks.

anybody? its been really bugging me.

I didnt think that would work... but the switches arnt open when the doors are closed so when one is opened.... lol Thanks alot man! But what if the circuit is live when the doors are closed? Guess I'll go pop one out and see if the dome light comes on if the 2 wires are connected or separated.

civic should have negative door switches.  Meaning in closes the switch to ground when the door is opened. Put the switches in parrallel to each other ( before the door side).  That should work fine.  I did a install a long time back in a 93 and there was a dsh light to signal open trunk, i used that and tied into the hood switch wire through a relay to change polarity if I remeber right.a true canadian eh!