Compare Pivot Table Columns to show Percentage Change

Hello All,
I've been attempting to make some comparison's in a Pivot Table but have run into some struggles. I have a PT setup in Excel 2016 with 2 columns "Month" and "Year", and they columns represent sales data for their respective months and states in a corresponding row. As such I would like to demonstrate in my PT the Percentage Change of that month between the years. I have attempted to add an additional "sales" line to the values section.Here is have selected "Summarize values by>Sum" and "Show Values As" >"% Difference From". I have selected the Base field as "Year" and the Base Item as "Previous" I also attempted to try the latter with Base Field "Month" and Base Item "previous" neither of which are functioning. Any help or guidance is always appreciated.

I have linked two images. First what I have and second what I would like to accomplish. I basically need to remove the extra columns denoted by the arrows in the screenshot.

1. https://www.evernote.com/shard/s101/...465753da57e213
2. https://www.evernote.com/shard/s101/...75eae9ee27cadb



Thanks in advance for your help!

Best :: CD

See my proposal with the field computing