Complex combination lock door set

Title: Complex combination lock door set
Hi,
I have been working on a system that uses 1 computer and 2 separate monitors to control access to my nuclear plant on my server. I have completed most of the code, and I know how to complete the rest, but I am stumped on one thing. How to determine which monitor the combination that is being entered is coming from.
Code: pastebin.com/uDk2knCt

I would appreciate it if someone could help me out.

I want to be able to tell which monitor a combination is being entered from so that I can control how many people are in the plant at one time.

http://computercraft.info/wiki/Monitor_touch_(event)

The first parameter from the monitor_touch event is the side of the monitor being touched.