EVENT_INVENTORY_SINGLE_SLOT_UPDATE (integer eventCode, integer bagId, integer slotIndex, boolean isNewItem, integer itemSoundCategory, integer updateReason)

check that bagId == BAG_WORN before anything else?
not sure if it informs of a newly emptied slot though.


edit : inventory item border is also using this : EVENT_ACTIVE_WEAPON_PAIR_CHANGED
might be useful.