I posted about casting CL on multiple target a long time before I even had CL, but I havent actually implemented this yet:

/targetenemy, /targetfriend
These commands cycle through the specified type of unit. /targetenemy is like pressing TAB, and /targetfriend is like pressing CTRL-TAB. You can also add a parameter of 1 which reverses the direction of the cycle (/targetenemy 1 is like pressing SHIFT-TAB).
Note: You can only use these commands once per macro.

/targetenemy
/targetenemy 1

/targetfriend
/targetfriend 1

So, theoretically, you could make a CL macro for random targets like this

Main: (whatever you have clicked)
/cast Chain Lightning

2 of your alts:
/targetenemy
/Cast Chain Lighting

2 of your alts:
/targetenemy 1
/Cast Chain Lighting


This would theoretically grab a maximum of 3 targets.