If I'm not mistaken, the calculations in pivot tables are limited to basic statistical functions like SUM, MAX, VAR. As such, I am at my wit's end how you can do this with the canned pivot table.

It can be done, however, by making the table on your own using SUMPRODUCT functions. This is easy, however it would require you to maintain a complete list of product numbers. It seems to me, based on your previous responses, that you want a completely automated solution so I'll leave it to you to design this if you want it or if you need help let me know.

Other than that, I've reached my level of incompetence with regard to pivot tables so it may just be a case that elicits the bit of sage advice that Mick Jagger offered in a song that begins with "I saw her today at the reception, a glass of wine in her hand."