Selling items using upgrades?

Hi,
I'm trying to get a structure that belongs to a player to sell an item ONLY after that specific item has been researched using an upgrade (not a structure tier). Can this be done, and in that case, how? I've tried using every tecnique I know, and also using the neutral shop triggers (I turned the structure neutral and then player-controlled again). Thanks in advance,

//Morre

EDIT: Never mind, I figured it out. I had to use "Items made" instead of "Items sold" in the shop.