i need help with a spell

[cursedrobbo]

i'm kinda noob but i was wondering if some 1 can show me how to make a chance on hit spell for me like a passive spell so it just need to get the % to work

10% chance on hit, cast chain lightning

it like the Dota Wep Mjollnir (20% Chance Chain Lightning)

but i want a passive spell not a item spell, can some 1 help me

 

[cursedrobbo]

i got the spell working but auto attack wont tigger it but if i click on a mob it will cast it, what the bug?