Creating an array to hold group sums

[antipodesman]

I am creating several subreports that list group (annual)sums but also compare sums in each year with the previous year. In order to do this I would like to store annual sums in an array. Could someone describe the steps required to create the array and then sequentially store the sum from each group in the array. If there is a better way to compare group sums I would be glad to hear about it.