Relationship with a Save historical data
I am usning FileMakerPro v12 and I need to create a relational databse so one file can have a list of products and prices. In a second file I want to have invoices that includes a place to enter a product and the price automatically populates. The issue I have and need to change is that if the price in the first file changes in the future I do not want every old invlice to show the new price but the price should be unchanged from when it was first listed. Currently everytime I adjust a price in the price file it triggers a change on every invoice in the invoice file. A second consequence is that if someone changes a price on a populated invoice it changes the price back in the products file which then changes all occurences on every invoice with that item. I need to set the relationship so it is not doing this. Any suggestions appreciated.