Reversing a list in Excel within a formula

Question

So there are a bunch of ways to reverse a list to turn it into a new list, using helper columns. I\'ve written some code that does use helper columns to reverse a list and t

Answer 1

This will do what you are asking:

=SUMPRODUCT(INDEX(A:A,N(IF(1,{3;2;1}))),B1:B3)

To make a little more dynamic you can use this array formula:

=SUM(INDEX(A:A,N(IF(1,LARGE(ROW(A1:A3),ROW(A1:A3)))))*B1:B3)

Being an array formula, it needs to be confirmed with Ctrl-Shift-Enter, instead of Enter when exiting Edit mode.