Hey Jack,
Off the cuff, I would say that the calculation wouldn’t be made until the product is connected to the stockist, therefore neither Airtable or Stacker would know what discount to make visible …
However, if your discount is connected to a category of stockists, then you could create a calculation field in your product table based on that category. Once you do that, then assign your stockist that category, and then you can use a conditional visibility to choose which calculation field to show based on the category of the logged-in stockist.
Hope that makes sense. If not, feel free to reach out again. 