In the following, I am summing a horizontal range in an array that changes or
gets extended each month. The formula looks at this month's date and then
matches it to the correct column. Then it sums the row from the beginning
date to through the new month.

If I use the index formula as it is here, it does not increment the row
number when it gets copied down the sheet:

=IF(A35<=$O$3,+N35-SUM(U35:INDEX($U$4:BP172,1,MATCH($O$3,$U$4:BP$4,1) ,1)),0)

If I add Row(), it doesn't return the correct total.

If I add Row(##), it works only if I start the numbering 3 rows before the
actual row used.

=IF(A35<=$O$3,+N35-SUM(U35:INDEX($U$4:BP172,ROW(P32),MATCH($O$3,$U$4:
BP$4,1),1)),0)

In this last formula, the row is actually row 35, but I used row 32 and got
the correct total.

Does anyone know what's wrong with the formula? Thanks.