Calculating percent change in Excel Pivot Table

Using standard Excel 2010 I am trying to calculate percent change from the years 2013 to 2014 and put that in a column after grand total.

The formula I am trying to use is (2013 - 2014) / 2013

I have tried Calculated Field but that hasn't worked, and I can't do Calculated Item since I grouped my dates to show in years instead of days. Does anyone know how I can go about calculating the percent change?

p-table.png

Any and all help is appreciated!