Procedure for dropped item

Hello,

i simpley want to call a procedure when a mob was killed. But its jsut impossible and makes no sense.
My procedure just adds a tag to the dropped items from the mob.

When i try to call this procedure after a mob is killed i get the error "you have selected external trigger that does not provide the following dependencies: itemstack"

that totally makes no sense because it is setting up tags for itemstacks...

I dont understand anyways, why dropped items from killed mobs or loottables arent "Item is dropped" in a procedure...

http://autosyn.eu/temp/mc_err_1

http://autosyn.eu/temp/mc_proc_1