IDs and consistancy between versions
I'm working up a solution that uses several pop-up fields. It is certain that the products populating those fields, along with their position in a list will change over time. So for example:
1. In 2014 there might be products A to M but by 2015 products B, F, J-K had been dropped and N-Q added. or
2. In 2015 products G+H were still present with the same name, but have a different composition.
What methods might be used to:
1. Update a product list but permit calculations with obsolete products for older record or at least keep the values generated from those calculations.
2. Ensure calculations occur based on the corrrect product (ie. a calc from 2014 should be with the 2014 product, not the updated 2015 one).