Triggered spell help!

Hi. I'm trying to make a triggered spell using starfall. Basicly I want the targeted units to have some special effects attached to them, And a Chain Lightning sort of effect coming off the targeted units. To do this I need to make a variable that holds the targeted units. But I can't find the way to set it.
Set Targeted_units = ?. Thx in advance.

Targeted_units is the units Targeted by the starfall.

Use a unit group. Unit groups can go beyond 12, its just that unit group orders only work for 12.