I think you will never get an answer to your question! Why???
- You do not provide your current working (not working code).
- You do not describe your project setup (which elements are used for example).
- You also do not describe in detail the flow of your project.
And on the top, working with APPs, → you are talking about → PRODUCT-PAGE ← → and this is a part of the → Wix-Stores-App <–, not everything is possible, when working with predefined apps.
Take a look in the VELO-API-DOCS, and find all provided APIs, which hits your situation.