1. Create a systems module dimensioned only by product. Add a list formatted line item set to the product list. In the formula bar select the first item from the product list. This will result in Product A being allocated against all products. Reference this in your target module.
2. Add a new line item to your product system module. Format this as the product list too and call it 'New Product'. Populate each entry with the correct product for the corresponding list item. In your target module use the following =IF TargetModule.New Product = ProductSystemModule.New Product then "OK" ELSE "NOK"
Could you explain the logic a bit, its not clear how either "First Product of the chain" or "Warning" are decided. Also I recommend using either a boolean or a list formatted line item for "Warning", avoid using text.
In fact, we have a list of products and we want to replace it for example: We have : A replaced by B then B replaced by C and C replaced by D what makes a chain of substitution A-B-C-D. What I want to display on each line is the first product of the chain in our case "A".For the warning, we cannot replace the same product twice, for example we cannot have A replaced by B and G replaced by A.