Have read the discussion strings and tutorials on Self-Joins and can't find answer to my specific issue.
Project - Equivalent to a typical Invoicing solution. Have an invoice for a specific customer with a portal for invoice line items (4 tables, customers, invoices, invoice line items and products all with standard primary and foreign keys set up). Products include a name and a size/type..
User Request - When they key in a new invoice line item they want to see a field to tell them how many of that product + size/type combination have they ordered/bought (e.g. this would be different for each customer and each instance in the Invoice Line Item Table).
Following the Self Join threads I was able to set up the new relationship and although I followed Answer ID: 3071 in Filemaker Support, the Self Join and result doesn't seem to work. I believe because some of the data is "unstored", specifically the Product Name, may be the issue.
I apologize if this is simplistic. Just my first project with Filemaker Pro 12