Hover mouse over bottom right corner of cell with formula in it and click and drag down to copy and paste the formula. Would also have column c as profit and d as roi (that's what I have anyway, but I do one line for each sng and also include date, site, time, etc).

Also recommend looking into pivot tables-they're excellent for quickly tabulating any data you may want to drill into.

Sorry for short reply as on phone and half asleep.