Make a new ability from the item ability: Item Armor Bonus (+1) to some levels, and set them to -1, -2, -3, etc. until you think it's enough.
Name it "Decrease"
Then add a trigger:
Trigger:
Decrease
Events
Conditions
(Current order of (Damage source)) Equal to (Order(attack))
[Your conditions]
Actions
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
If - Conditions
(Level of Decrease for (Triggering unit)) Equal to 0
Then - Actions
Unit - Add Decrease to (Triggering unit)
Else - Actions
Unit - Increase level of Decrease for (Triggering unit)
this trigger:
Trigger:
Initialization
Events
Map Initialization
Conditions
Actions
Set UG = (Units in (Playable map area))
Unit Group - Pick every unit in UG and do (Actions)
Loop - Actions
Trigger - Add to Decrease <gen> the event (Unit - (Picked unit) Takes damage)
Custom script: call DestroyGroup(udg_UG)
and this trigger:
Trigger:
Initialization2
Events
Unit - A unit enters (Playable map area)
Conditions
Actions
Trigger - Add to Melee Initialization <gen> the event (Unit - (Entering unit) Takes damage)
And you must have another trigger to remove the ability once the effect of -armor is gone.
Don't forget for [Your conditions]
If there's nothing added, then everyone could deduct everyone's armor with the attack order.
It is still not a reliable way of detecting attack damage, if the attacker would have for example immolition that hurt the attacked unit while attacking it then the immolition damage would trigger the trigger aswell.
You should insted give the attacker a buffplacer like a frost attack and then you check if the unit as a specific buff when he takes damage insted of checking the current order.
i think you should create a skill like inner fire which grants armour deduction instead.
e.g. lvl 1 -1 armour, lvl 2 -2 armour. you have to allow negative values in the editor preferences before you can key in negative values. So everytime the unit is attacked u can cast the 'inner fire' on the unit attacked. you can set the lvl of the inner fire cast by the dummy as well.
however you have to use a buff related attack just like mr-death suggests. or else a true attack on the unit cannot be detected.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.