Sorry I should clarified.
Similar, to how Excel calculates YTD but at of each month. So the yellow line below is the YTD and shows what the YTD % is reflecting prior month and that current month.
So for Feb, it shows the YTD & for Jan and Feb at end of Feb. March would show Jan, Feb, March, etc. The Actual YTD would obviously be the last point.
Can you provide a sample workbook?
Might be difficult at the moment. I'm currently using data on a Tableau Server at my company.
I can work on creating something with fake data to attach.