Is there a way to carry a group total (calculated in the group footer) forward into the footer for the next group so that it can be used in a calculation to provide the % change between the 2 groups?

Suppose the report is grouped on year, with columns for each month. In the footer for 2008 we want the calculate the % change for jan08 over jan07.

IE result = (jan08grouptotal - jan07grouptotal) / jan07grouptotal

Thanks