I was using the VFP's RI code generator to cascade my updates. So when my parent record is deleted my child record will be too and when my parent is changed my child will reflect that change automatically. My one-to-many relationship is based on an expression PO+REFNUM. When I choose to generate my RI code I get a message saying:

"Cascade updates based on expression-based index keys may not behave as expected."

Does anyone know more about this? What are the possible pitfalls here? I know the best way to do this would be to have the tables related by a seperate ID field, but we can't add any fields to our table at this point.