Digital Product Automatic Upgrade Discount

[hongkong]

Hello! Part of my online store sells digital downloads and one of the products comes in three sizes. Call them basic, advanced and pro. Many users buy the basic version and want to later upgrade to pro. I end up having to create a custom discount code for them. Is there a way to ID customers who have already purchased the basic version and then give them automatic discounts to the advanced and pro versions when they come to the store?

I know I can do this through email automation but most websites that sell software make it much easier to upgrade than I'm finding it to work for my Shopify customers.