Formula Query on report record set

How to find duplicate values in a report record set?  I'm working with a product BOM (bill of material) table that is joined by Product ID.  Each Product ID has its own BOM structure which includes part numbers.  The BOM table will have duplicate part numbers.  Example, a part number could be in the BOM table 14 times (used on 14 Product ID's).  When I run a BOM comparison report, filters by "ask the user" for Product ID (#247) vs Product ID (#280).  The report pulls all the records for both Product ID's, which includes duplicate value at times.
How to identify if a part is a duplicate in this report only?

Thx
Jim

------------------------------
James Blackford
------------------------------