It depends on the item type(equipable or special/various). Either way, create a global, something like gb_wand_charges. Have an event linked to equipping the item that has a conditional. The conditional should check if the global is equal to zero. If it is, it means that it's the first time the item has been equipped. However, it could also be because the item is out of charges. You could solve this by having the item self-destruct when it's charges are spent. Back to the event: If gb_wand_charges=0, then set gb_wand_charges to, let's say 10. Then, have the spell event link subtract 1 from gb_wand_charges. Then put gb_wand_charges in the description of the item(I've tested it. Variables do work in descriptions.) In the spell event link, also have a conditional that checks to see if gb_wand_charges=0. If it's true, have an item wizard that drops the item(could also add a new one that says charges are spent).
Hope that's not too confusing.
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They say money can't buy happiness, but it's not happiness I want. It's money. -Zippy