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
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.