I'm creating a .NET crystal report sales report that lists the total # of each item sold and the percentage of total sales that the item contributed towards however, before I can calculate the percentage for each row, I need to know the total qty of the report, which I don't know how to retrieve.

So a sample report of 500 items sold may look like this:
-----------------------------------------------------------
Category | Qty Sold | Percentage
-----------------------------------------------------------
Electronics | 200 | 40%
Books | 100 | 20%
Movies | 150 | 30%
Games | 50 | 10%
-----------------------------------------------------------
Total | 500 | 100%
-----------------------------------------------------------

How can I calculate a percentage for something like this?
Thanks.

-Goalie35