Sum Every Second, Third, or Nth Row or Cell
Every now and then you might want to sum every second, third, fourth, etc, cell in a spreadsheet. Now you can, with the following tutorial.
Excel has no standard function that will sum every nth cell or row. However, you can accomplish this in a number of different ways. All these approaches use the ROW function and the MOD function.
The ROW function returns the row number of a single cell reference:
ROW(reference)
The MOD function returns the remainder after number is divided by divisor:
MOD(number,divisor)
Nest the ROW function within the MOD function (to supply the number argument), divide it by 2 (to sum every second cell), and check to see whether the result is 0 (zero). If it is, the cell is summed.
You can use these functions in numerous ways-some of them producing better results than others.