Maybe your formula works only if D04_x is always present in column D. But, as
I written, if it change position ? So it would be a flexible formula that
keeps in consideration this aspect.
Thanks




Assuming that your columns of dates is column A and that your columns
of D04_x is column D, and that the data starts on row 3 i those
columns, you may try the following formula:

=SUMPRODUCT((MONTH(A3:A100)=MONTH(INDEX(A1:A100,MA X(NOT(ISBLANK(A3:A100))*(ROW(A3:A100))))))*(D3:D10 0))

change the 100 on four places to fit the number of rows with data that
you have. Note that the A1 should not be changed.

The formula will return the sum of D04_x for those rows that have the
same month as the last date entered in column A.

Hope this helps / Lars-Åke