[Trigger] help with trigger with specif unit event

[fengar]

i want to make a hero that when he use a skill it replace that hero with other and when the last replaced unit take some damage it replace it again for the first unit, the trouble is that the event takes damage is on specific unit event but i can't use the last replaced unit like the specific unit

 

[Bubba Ex]

May seem a little complicated but paste following script into your map header

function TRAUTD_Actions takes nothing returns nothing
    local integer i = 0
    loop
        call TriggerRegisterUnitEvent(udg_t[i],GetTriggerUnit(),EVENT_UNIT_ATTACKED)
        set i = i+1
        exitwhen i >= JASS_MAX_ARRAY_SIZE
    endloop
endfunction

function TriggerRegisterAnyUnitTakesDamage takes trigger t returns nothing
    local integer max = CountUnitsInGroup(GetUnitsInRectAll(bj_mapInitialPlayableArea))
    local integer i = 0
    local unit u = null
    local group g = CreateGroup()
    local trigger t2 = CreateTrigger()
    call GroupAddGroup(GetUnitsInRectAll(bj_mapInitialPlayableArea),g)
    loop
        exitwhen i == max
        set u = FirstOfGroup(g)
        call TriggerRegisterUnitEvent(t,u,EVENT_UNIT_ATTACKED)
        call GroupRemoveUnit(g,u)
        set u = null
    endloop
    set udg_t[udg_index] = t
    set udg_index = udg_index+1
    call TriggerAddAction(t2, function TRAUTD_Actions)
    call TriggerRegisterEnterRectSimple(t2,bj_mapInitialPlayableArea)
    set g = null
endfunction

then to use it do following in an initialization trigger.

• Custom script - Custom script: call TriggerRegisterAnyUnitTakesDamage(CHANGE THIS)

Change the bit that says CHANGE THIS to gg_trg_MyTrigger(MyTrigger = your trigger name). Remember to replace spaces with underscores (_).

If you experience any problems with this just let me know and I'll sort them out.

EDIT:
requires 2 global variables:

t = trigger array
index = integer