Can someone show me how to make a trigger that detects every time raynor (marine), duran, and gui montag shoots with EUDs? I really would like to use this for a map that I'm making.

http://farty1billion.dyndns.org/EUDDB/?pg=ref&a=unitnode
If you can't figure out how to do it with the information I've given you, click on the EUD links in the sticky, and learn more about EUDs. I don't have time right now to make you a trigger.

+0x64 - CUNIT* AttackingUnit

Also, take a gander at halloween priest, and http://www.staredit.net/?attachment=3202

The offset you gave was an entry in the CWEAPON struct, not the CUNIT struct... Anyway, even if that was in the CUNIT struct, just because you have a unit targeted to be attacked doesn't mean you are attacking it at that time. Use:
+0x55 - BYTE bGroundWeaponCooldown
+0x56 - BYTE bAirWeaponCooldown

If its >0 the unit has attacked and is waiting for the cooldown to attack again.

I hadn't looked into it, that was just one location I thought might work. cooldown makes more sense.

O.o I'm sorry, but the only thing I know how to do with EUDs is detect how much HP a unit has. XD I honestly don't understand anything you guys are saying.

You're one step there, If you know the unit HP, then you know the unit's HP address. From there, add the difference to the address to find the unit cooldown (It's 0x55 and 0x56 more than the start of the unit). If you can't figure this out, it's probably not for you.

Wait, what? What do you mean by "add the difference"? I found the address for Jim Raynor (Marine), but I'm confused as to what I should do now.

you found the address for Unit 1. Unit 1 has a number in it which says exactly what unit it is (00 00 would be terran marine). Now you need to add in 56 and subtract whatever the hp offset is. Open up artmoney, go to the memory address, and see if you can figure out where everything is based on that link I gave you, and watch the numbers change as you have the unit attacking someone/taking damage.