passive abilitys

Is there any way to detect when a passive ability casts?
i mean, let's say critical strike, is there anyway to detect when it effects?

There are some methods, but it is generally considered much easier to just trigger the ability completely.

let's say i am trying to make a counter attack, wich sepuse to treat more dmg when the attacker has evaded an attack, so i though of giving unit an evade skill, now when it has evaded an attack, i will buff the unit with a buff for 1 second, the counter attack it self will check if a unit has that buff when it casts, and will inflect more dmg :\
so..
what do u mean by triggering the ability completely? how can i trigger an evade skill

With this.