If there are duplicates, select which to keep.

[Applemdjs311]

If upc is a duplicate, specify which row to keep based on another attribute.

Ex: If upc is duplicate, keep the row that is NOT brand x. But if the upc is not a duplicate keep whatever product shows.

Upc    Product     
123    Yellow boat       - want to keep
123    Brand x          - want to get rid of this row
234   Green bear        - want to keep
789    Brand x                - want to keep

[sdf]

for the UPC you can use :
total(1 for [Upc]) <--number of occurrences

create a case statement for your Product base on above.
some like if Upc count > 1 then [Filtered product] <--- does not include brand x (i think you can use except)
else [Product]

haven't tried this though just an idea.