If I understand Lookup right, it is going to take the highest number closest
to what you provide. So by providing an outrageously large number, it will
take the highest number it finds. In this specific example I think it will
work for me, but I have other spreadsheets where the monthly value may be
negative so the cumulative value actually decreases. In this example the
lookup formula provided wouldn't work because it would return the month
before (because of the negative value) since it was the greater of the two.
What would I do in this case?

"Carpie" wrote:

A1:A13 is January-December and Total. B1:B13 is the GOAL numbers. C1:C13
are the ACTUAL numbers. The numbers entered in the cells of row C are
aggregates (they include the amount of the previous months). I want C13 to
be the last number entered in that row (which will also be the last month in
which an actual was entered). Is there any formula that looks at those 12
cells and takes the farthest to the right?