Put this one line formula in a columndrag to the right two columnsselect
the three formulas and drag to copy down 12 rows

=SUMPRODUCT((YEAR($A$1:$A$400)=COLUMN(A1)+2003)*(M ONTH($A$1:$A$400)=ROW(A1))*$B$1:$B$400)

--
Don Guillett
Microsoft MVP Excel
SalesAid Software

"Motaad" wrote in message
...
I have a spread sheet with three years of monthly data. I need to
calculate
for a rolling twelve month total each month.
(i.e.)
sum data in columns for (Jan2006 - Dec2006),
sum data in columns for (Feb2006. - Jan2007),
sum data in columns for (Mar2006. - Feb2007, etc.)

--progressing the total along twelve months each new month. Any ideas
--
Motaad