Clarity on part of a formula

Originally Posted by DonkeyOte

(from this thread)
If you create a running total you should be able to do it relatively easily I think.

eg

E2: =SUM(C1,E1)
copy down for all rows (ie to E28)

Formula to generate list then:

J2: =LOOKUP(ROWS(J$2:J2)-1,$E$2:$E$28,A$2:A$28)
copy to K2
copy J2:K2 down as far as required

question from noob

May i know what is this for?

ROWS(J$2:J2)-1

Try putting that in a cell as a formula and then copy that cell downward:

=ROWS(J$2:J2)-1

The number of rows in the range J2:J2 is 1, minus 1 = 0, so the first formula resolves to zero. But as the formula is copied down the range expands to encompass more rows making the numbers increase.

In a nutshell, this is one of many ways to cause a formula to give a set of sequential numbers as it progresses down a column.