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