@TAGORTII just stuck with your warning message. Do i understand correctly that the order of the list members matters in calculation? I can see in your example that error message is only against "I" because NEW PRODUCT mentionned there is "G". And "G" stays prior to "I". I am asking because if we ignore the error, then the chain will look like this: I-G-J, which can be calculated as FIRST PRODUCT OF THE CHAIN = "I".
Or this means that error appears only if any product mentionned more that once?
If this is actually the case then you have to concider the above in your calculation.
The order of the new product assignment and the occurrence of the new products differs from the first case. If I already substituted a product i cannot used as a new product. Did you find a solution for the first part of the requirement ?