Add ability trigger

Add ability trigger

im trying to make spell that adds an ability to your own and your alliys units for a limited time. I have made trigger to try making this spell but it doesn't work so i need some help learn something new

here is my trigger

Unit - A unit Begins casting an ability
Conditions
(Ability being cast) Equal to Howl
Actions
Unit Group - Pick every unit in (Units within 500.00 of (Position of (Casting unit)) matching (((Picked unit) belongs to an enemy of (Owner of (Casting unit))) Not equal to True)) and do (Actions)
Loop - Actions
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
If - Conditions
((Picked unit) belongs to an enemy of (Owner of (Casting unit))) Not equal to True
Then - Actions
Unit - Add Evasion to (Picked unit)
Wait 15.00 seconds
Unit - Remove Evasion from (Picked unit)
Else - Actions
Do nothing

this is what i would do

Unit - A unit Begins casting an ability
Conditions
(Ability being cast) Equal to Howl
Actions
Unit Group - Pick every unit in (Units within 500.00 of (Position of (triggering unit)) matching (((matching unit[probably part u messed up]) belongs to an enemy of (Owner of (triggering unit))) Not equal to True)) and do (Actions)
Loop - Actions
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
If - Conditions
((Picked unit) belongs to an enemy of (Owner of (triggering unit))) Not equal to True
Then - Actions
Unit - Add Evasion to (Picked unit)
Wait 15.00 seconds
Unit - Remove Evasion from (Picked unit)
Else - Actions
Do nothing[/code]

thanks your're really helpful now the picked units get the ability i want but there is one little problem the ability doesn't get removed after 15 seconds it stays there forever