problem with ability based on shockwave

[Zemeio!]

well, heres what i have
an ability (sonic wave) based on shockwave, i dont want 2 do the damage of the ability with the object editor, i want 2 do it by trigger cuz it will b based on somethings.. how could i make the damage for that?, which event and conditions?

ty for all the help : )

 

[DM Cross]

Events would be:
A unit begins casting a spell.
The conditions could be any of the following:
Casting unit is equal to <whatever unit uses this>
Ability being cast is equal to <whatever you call it>

Then the actions I'm sure you can work out for yourself. (However, if you can't, feel free to ask! )