is it possible to index a cell and then sum that cell plus every other cell behind it in that row
This example shows you how to create an array formula that sums every nth row in Excel. We will show it for n = 3, but you can do this for any number. 1. The ROW function returns the row number of a cell. 2. The MOD function gives the remainder of a division. For example, for the first row, MOD(1,3) equals 1. 1 is divided by 3 (0 times) to give a remainder of 1.