I wnat to add a difference calculation to a Pivot Template. However I do not have a seperate source field for 2011 and 2012. The data comes from 1 colum in the data source. See below. How would I insert a field in the Pivot Table taht can then be sorted? Thanks

Month (Multiple Items)

Sum of Total Extended Cost Amt - Sum Year
Customer GL Dept Num Generic Name 2011 2012
712401 CALCIUM CARB/VIT D3 $2.11 $2.11
CALCIUM CHLORIDE $77.00 -$77.00
DEXTROSE/WATER $200.37 -$200.37
HETASTARCH/NACL $211.76 $129.90 -$81.86