Adding % Change Calculated Field

Hi Excel Geniuses,

Any advice on how best to integrate this percent change formula into my pivot table?

I am streamlining a co-worker's report but realizing that I have taken more difficult routes than what is probably neccessary. I would like this to update automatically and preferrably use a less-messy calculated field. I do not know much about these.

Thanks in advance.

You Rock,

Lindsay