Setting Each Target of Chain Lightning

Ok, i want to base a spell of chain lightning (because it can hit multiple units in a chain), but i'm having a heck of a time trying to figure out how i would trigger and define each target that chain lightning hits. This is the spell, and i know how to use triggers to deal damage, but i'm clueless on defining each target:

Inflicts 25% of Wrenches current health in damage, drains 20% of Wrenches current mana from the target. Each leap reduces the bolt's effectiveness by 6%. Leaps 3 times.

There definantly is a way, Hivemind sent me a PM ages ago about how to do it, but that msg has long since been deleted. You could try PMing him about it, but I dont think hes around anymore. Somone else should know though

I think that can be done by triggers. Therefore you need to pick random targets with the trigger. (and for the nice arts, you will also need to make dummy casters to make it look like the chain.)

If you don't understand me, PM please. I will explain it further, or even make it if I have the time.

Sorry for dubble posting, but I just wanted to say than on my site there is a map you might want to look at. It is a chain spell, but it is mady by triggers, so you can edit it to your wish.