Heros wont use their abilities on each other

I am making a cinimatic for a screen shot i need and i need a DK to use Death Coil on the Paly and a Paly to use Holy light on the DK. when I tryed to do it the DK just died. Can you help me?

did u do it, create unit, order last created unit to do "spell"...

if not thats how u do it, also holylight may kill a dk

Yeah I figured it out right before you replyed. Thnx anyway.