How to make abilities scale off attack damage

[Sham]

I somewhat know where to start on this, I've used Arithmatic and such before, but I'm not sure exactly how I go about this...

How would I make, say, Firebolt deal damage based on my attack damage? Like my attack damage x3. Obviously I'd need some dummies and whatnot, besides that what do I do?

 

[Meticulous]

Short answer: You can't.

Long answer: You have to track every single buff, ability, item, etc. that boosts attack damage, along with the base damage and primary attribute bonus of all of your heroes, and add it all together.

 

[ForeverBeADragon]

Just make an illusion with 300% attack damage.