I have a pivot table with the categories of Sales, Cost, Profit, and Profit Margin. However, I can't seem to list the Profit Margin category to list as a Percentage of the total sales (In other words, as an actual Profit Margin). To get this column, I simply drag Profit into the values column again and try to change it to % of sales. Every time I try to do this, however, I never get to choose the sum of the sales, but rather individual items that make up the pivot table.

Is there any way to list a total profit margin percentage on a pivot table? Any help on this matter would be greatly appreciated.