Quest to make mobs with exp drop something extra

[Domingodarkrage]

I'm working on adding a daily quest to my server, where the players can get the quest once per day. Any mob they kill worth experience will have a chance to drop an additional item or summon an item to the player (or increase a counter). I know I could use the task system for select mobs, or write perl codes for select mobs, but I want the players to have an open ended opportunity on how they go about this quest: zone and player levels do not matter.

I'm hoping to use the global.player script, but I've yet to figure a way on how to get this rolling forward- I cant figure out how to determine if the player is getting experience from a kill.

Any suggestions? I was hoping there was an EVENT_NPC_SLAY that triggered when the PC did the slaying (from global.player) as opposed to the NPC, but that is not in our code.