If you are using Microsoft Excel to manage numerical data, at some point you're inevitably going to display percentages. Doing so can give you a new insight, or make summarizing heaps of data a bit ...

What <B>Manus</B> said, although it'd most likely work better for you if you worked horizontally rather than vertically. A1 would be the sales, B1 would be the division formula, and C1 would subtract ...