Looking for user tracking script

I am developing a website in which under particular videos users can go to an affiliated e-commerce where they can find video products to purchase. We have an agreement with this e-commerce but I want to develop a tool which could track users that go on this e-commerce from the link under the video and track how much the user spends (like a tracking pixel), because I want a further attestation of payments, if you understand me! Any tip on how can I do it?

Thank you