Scripts

it won't work. It's hard to explain, but the functions of the combat script imply a single action/cast; here, there are actually two (selecting the enchanted arrow + selecting the spell). That is, there is no suitable function. For the same reason, you cannot, for example, cast teleport with a script (selecting a target + selecting a location). But you can try to emulate the arrow action - first, cast a rain of arrows, and then the desired spell on the units that will take damage after the volley.