Here is my situation.  I'm trying to produce a report that will show a percentage increase or decrease on the average value of our invoices by year.  I currently have a report grouped by year that shows me the average value of the invoices for that year.  How do I reference the average value from a prior year to calculate the percent change for the current year.  For eaxmaple:

 

 

2005     530.00                                          <-----group Header Level

2006     526.00                -0.75%               <-----group Header Level

2007     382.00                -27.38%             <-----group Header Level

2008     270.00                -29.32%             <-----group Header Level

 

Any help would be greatly appreciated.

 

Thanks in advance.