Using Choas Ability

For my RPG, I have an ability based on Chaos ability that I made it to change a hero into another hero.
However, once I change the hero with the skill, the new hero has the exact same skill, based on chaos, to turn the hero into the same hero.
Is there a way to get rid of the same ability after a hero becomes a new hero?

Try removing the ability using the Unit - Remove Ability, then add an ability which will turn him back or whatever.

Mmm... Let me explain better.
I am basically making a class system.
Once a hero reaches certain level, the hero will be click on, let's say, Warrior (based on Chaos ability). That will transform the hero into a warrior. However, once the hero becomes a warrior, he is still able to learn the ability Warrior again even though the hero already is a warrior. I made a simple trigger. It doesn't seem to work though...

Sorry, I don't know how to use the trigger tag so I'll just post the text.

First Tier
Events
Unit - A unit Learns a skill
Conditions
Or - Any (Conditions) are true
Conditions
(Ability being cast) Equal to Mage Human
(Ability being cast) Equal to Mage Murloc
(Ability being cast) Equal to Mage Orc
(Ability being cast) Equal to Warrior Human
(Ability being cast) Equal to Warrior Murloc
(Ability being cast) Equal to Warrior Orc
Actions
Unit - Remove Mage Human from (Learning Hero)
Unit - Remove Mage Murloc from (Learning Hero)
Unit - Remove Mage Orc from (Learning Hero)
Unit - Remove Warrior Human from (Learning Hero)
Unit - Remove Warrior Murloc from (Learning Hero)
Unit - Remove Warrior Orc from (Learning Hero)