Need help making targeted unit invunrable

how would i got about doing this. I based the spell of Innerfire. I did some triggers but its not working. Anyone know whats wrong

well I use WEU and do this:

events- Advanced a unit is targeted by a spell.

Cond- ability being cast equal blah blah

Actions- Make (targeted unit) invulnerable.

edit: and just do the time period of it, you know....

i tried that and this is what i get *Bolded part is what was highlighted"

//===========================================================================
function InitTrig_Holy_Armour takes nothing returns nothing
set gg_trg_Holy_Armour = CreateTrigger( )
call AUnitIsTargetedByASpell( gg_trg_Holy_Armour )
call TriggerAddCondition( gg_trg_Holy_Armour, Condition( function Trig_Holy_Armour_Conditions ) )
call TriggerAddAction( gg_trg_Holy_Armour, function Trig_Holy_Armour_Actions )
endfunction

:bgrun: dunno then, I made a spell like that some time ago and it worked...