Do you have correct setup contenttypes? Is the Product field part of such contenttype? Then I would start with input WSC to check. 1. Read all Lists 2. go to every list check if this / these contenttype(s) exists 3. get all affected items with a query. Run the code for every item It's no big problem I think it just might take a little bit to run through all lists from one WSC and of course do this for every WSC you have to check.
SharePoint Consultant and Developer at acocon Author of Primary ROleplaying SysTem I'm the ninth in a row of seven!