Hello, Would anyone have any suggestions as to how I could create a 12-month running total by group? Below is an example of what I am trying to accomplish. Within the example there are two groups, A and B. Each row of data represents one month along with total cost per month. The variable I would like to calculate is the "12_Mos_Cost", which is the 12 month running total within the group. As you can see, the first 11 "12_Mos_Cost" is blank because there hasn't been 12 months of data yet. I have figured out how to create a 12 month running total, but have yet to figure out how to do this by group. Any suggestions would be most appreciated!!!! Thanks! Group Year Month Cost 12_Mos_Cost A 2009 1 $             5.00 A 2009 2 $             7.00 A 2009 3 $             4.00 A 2009 4 $           12.00 A 2009 5 $             9.00 A 2009 6 $           15.00 A 2009 7 $             8.00 A 2009 8 $             4.00 A 2009 9 $           13.00 A 2009 10 $             6.00 A 2009 11 $             7.00 A 2009 12 $           10.00 $            100.00 A 2010 1 $           14.00 $            109.00 A 2010 2 $             8.00 $            110.00 A 2010 3 $           17.00 $            123.00 A 2010 4 $           10.00 $            121.00 B 2009 1 $           15.00 B 2009 2 $           19.00 B 2009 3 $           16.00 B 2009 4 $           20.00 B 2009 5 $           14.00 B 2009 6 $           17.00 B 2009 7 $           11.00 B 2009 8 $            9.00 B 2009 9 $           18.00 B 2009 10 $           15.00 B 2009 11 $           13.00 B 2009 12 $             5.00 $            172.00 B 2010 1 $           16.00 $            173.00 B 2010 2 $           14.00 $            168.00 ... View more