Hi Brendon -

Sounds like you will need a third table. It can be called Invoice, or whatever makes sense to you. Then you would create a reference field to product and customer. You can add other fields that would make sense like date, etc.

Then when a customer orders something, you can find the customer in the customer table and in that record will be a view into the Invoice table where you can click the + Create Record text and add products that the customer asked for.

There is so much more you can do. Have you tried looking at the Invoice template Ninox provides?