Formula to sum sales for last YTD

Formula to sum sales for last YTD

Hi there, I'm looking for help with an aggregate formula to sum sales for last YTD.

I'm trying to create a report that will show the Months sales for 2019 and the TOTAL YTD for 2019 compared to Month sales in 2020 and the TOTAL YTD for 2020.

Any help would be appreciated.