Adding slow effect to normal attack or stun?

Hey, i have a tower and i want to add 30% chance of slow or stun, but i dont know how, i suppose i have to add a skill right?

Thanks

For Stun, just add the Bash ability to the tower.
For Slow, try messing around with Orb of Slow ability, I think it has % chance to trigger

Well, I guess you could make a trigger that runs whenever a unit attacks, check to see that it's the proper tower, then have a random integer between 1-10. Check to see if the integer is less than 4. if it is, make a dummy unit cripple an enemy using a customized cripple (this is for slowing). For the stunning, just give it a 30% chance bash w/o extra damage.

Die jacek, you beat me.