How do I get a value for the cumulative value of any given ratio? I am computing Manufacturing Profit Margin % = Manufacturing Profit / Total Sales. I am trying to write an expression that will sum compute the overall value by taking Manufacturing Profit 1 + Manufacturing Profit 2 +Manufacturing Profit 3 / Total Sales 1 + Total Sales 2 + Total Sales 3 = Cumulative Manufacturing Profit Margin % for periods 1-3. Any help?
