if the trigger executes a script i've made it so the unit that tripped the trigger is a globalvariable called globalunit, or something similiar. so if you put something like this in the script
? globalunit == unit1: goto "unit1"
? globalunit == unit2: goto "unit2"
? globalunit == unit3: goto "unit3"
you can go to different parts in the script, i don't know if this is any help to you because i'm still unsure of what your trying to do as I'm not used to scripting for multiplayer.