Calculate current month YTD minus previous month YTD

[bhaveshp90]

Hello,

I have the table as shown below with YTD and MTD as expressions.

MTD = (Current month YTD) - (Previous month YTD).

My expression for MTD = YTD - Alt(Above(Total(YTD)), 0).

This expression is calculating correctly when selecting individual project number, but for all the project numbers selected It is calculating on per row basis which is completely wrong as shown in the below image;

Any idea on how to avoid it? (I want to calculate MTD as current month YTD - previous month YTD per Project_Number)

attached are files for your reference;

thanks

[bhaveshp90]

It is not allowing to select 2016 and 2017 years, look at below;