I have a list of items that an account hold exported from an account
sytem as a text file. I am trying to generate not only what an account
owns but what the account doesn't own. (The accounting system will not
export what the account doesn't own.) I am looking for a rountine or
quick formula to compare what each account owns and add what is
doesn't. Here is an example assuming we only had 3 products.

Raw Data:
Account Quantity Product
1234 12 Product 1
1234 4 Product 3
4567 12 Product 2

Desired Output:
Account Quantity Product
1234 12 Product 1
1234 0 Product 2
1234 4 Product 3
4567 0 Product 1
4567 12 Product 2
4567 0 Product 3

Any help would be appreciated!