Emulate Critical Strike

[Majin]

Hi,
I need something to emulate the critical strike ability trough triggers when a certain ability is active (with active i mean like Heal or Inner Fire), i thought of various solutions but with my limited knowledge i'm not able to apply any.
At the moment i'm using only GUI but i promise in this weekend i'll learn JASS

 

[PurplePoot]

AnyUnitTakesDamage by Shadow1500

With that, some simple Jass knowledge, and an orb effect to make sure that the damage was dealt by an attack, recreating such a spell as critical strike should be easy.