How can i make This Work?

So I'm trying to make a command that enchants the weapon/item in hand. I put the item procedure "Add Enchantment with Level 1,000,000 to Provided Itemstack type (enchantment) under the default procedure block but with the global trigger as "Command Executed". But it says "You have selected external trigger that does not provide the following dependencies: itemstack.   Just wondering what that means. Thanks!