How to detect whether melee skill or attack was hit successfully?

I’m making the autobot for Assassin which can detect whether its casted melee skills (charge skills) or normal attack was hit the monster to make a counter for my own purpose (I am trying to edit the …/common/Attacks/Assassin.js and other related).
so far, I cannot find where and how to achieve that target.
So appreciate for your help.

I read somewhere in the support files that martial arts assassins aren’t supported because there’s no way to detect charges

I want do the samething, maybe we can change the way of thinking, not to detect the hit successful, detect the release skills’s damage has been changed.