Showing MTD and Prior MTD based on Working Day in the same chart

[schuffa]

Hello Power BI Community,

I'd like to show a dataseries by working day for the current + prior month in one chart. The tricky part is, that as each month can have different working days (WD), the correct sums by WD shows up. I had managed to overcome the topic showing the prior month data related the prior month WD by adding a separate working day table (DV_WD), linked to the WD column of the DV_Date table and using this piece of code: 

NS PMTWD = CALCULATE([NS],

FILTER(ALL(DV_Date),

DV_Date[Month_relative] = VALUES(DV_Date[Month_relative]) -1

&& DV_Date[WD] <= MAX(DV_WD[WD])

))
-> problem is now, that the evaluation does NOT stop with the Max WD of the respective Prior Month, but with the SELECTED month. This leads to incorrect results. Eg. selecting Feb'21 (18 WD's) the Jan'21 dataline stops as well on WD18 - even though Jan'21 had 20 WD's. So the last both data points are not shown.

Question is: How can I achieve to show also for the prior month ALL working days of the PM aside the WD's of the current month?
Any help is appreciated, please find the sample pbix with randomized numbers here: https://www.dropbox.com/s/oou9pk8h0kg7g5z/WD%20Problem.pbix?dl=0 

[PaulOlding · Accepted solution]

I think this video goes through a solution to this exact problem:

https://www.youtube.com/watch?v=nYH738VONi8