I am using dates as a parameter in a Sumproduct, they are formatted as
mmmm-yy but I am only using the last day of the month.

I want to add up everything within a 12 month period. How can I do this
using 'GREATER THAN' and 'LESS THEN OR EQUAL TO'.

So if the date is 31/03/2009, how can I add up everything within the date
range 30/04/2008 - 31/03/2009?

Currently I am doing it by identifying the row ranges for each period but
want the formula to be more dynamic in case things get added.

Thanks
Rick