acculated calculations

Hello, everyone. I need to perform an procedure in a report to get an accumlated result. The table layout is as following: col1 col2 col3 1 2% 2% 3 4% (1*2% + 3*4%)/(1+3) 5 6% (1*2% + 3*4% + 5*6%)/(1+3+5) 7 8% (1*2% + 3*4% + 5*6% + 7*8%)/(1+3+5+7) col3 involves the calculations from col1 and col2. What is the best way to write this report? Should I use a cursor or stored procedure? Could someone give me some point how to do this? Thanks. Tina.