I want to be able to have multiple records for each client but not allow duplicates of the same product selection for that client without having a separate application for each product. So, if a client wants 3 different products then there can be 3 different entries, but if the application participant tries to add the same client ID / Product combo then the application would reject the entry.
Entry 1 - ID#1002 & Pie (Good)
Entry 2 - ID#1002 & Chocolate (Good)
Entry 3 - ID#1002 & Pie (Rejected)
Note: Product selection is a dropdown list, so requiring a unique value in either field alone will not achieve the desired result.