Oh im sorry! I realized that i need a trigger on how to unlearn the specific spellbook ability from the hero using another normal ability when click or begins casting....pls help!!As far as I know, only 2 things can modify abilties of a unit/hero.
1: Object Editor: Can only change abilities in World Editor.
2: Triggers: Can only change abilities ingame.
So you need triggers for it to work. Why do you want to avoid using triggers?