Unit only effected by 1 spell?

[HG-Bonfire]

For a map i'm making, I need to set up a unit so it can only be hit by the Holy Light spell, and no other spells work or do any damage and no attacks work, is this possible?

 

[Nigerianrulz]

first make the unit immune to magic and invulnerable
then this trigger

FOR YOU
    Events
    Conditions
        (Triggering unit) Equal to Ghoul
    Actions
        If ((Ability being cast) Equal to Holy Light) then do (Unit - Cause Priest to damage Ghoul, dealing 500.00 damage of attack type Spells and damage type Normal) else do (Do nothing)

you can change the damage and damage type too