Subtract values from two rows in matrix

Hi  maart666 ,

Modify your measure as below:

Difference = 
VAR thisforecastnum =
    MIN ( Arkusz1[Forecast no] )
VAR thisforecast =
    SUM ( Arkusz1[Qty] )
var lastforecastnum=CALCULATE(MAX('Arkusz1'[Forecast no]),FILTER(ALLSELECTED(Arkusz1),'Arkusz1'[Forecast no]<MAX('Arkusz1'[Forecast no])))
VAR lastforecast =
    CALCULATE (
        SUM ( Arkusz1[Qty] ),
        Arkusz1[Forecast no] = lastforecastnum
    )
RETURN
    IF (
        ISBLANK ( lastforecast ),
        BLANK (),
        thisforecast - lastforecast
    )

And you will see:

For the related .pbix file,pls see attached.

Best Regards,
Kelly

Did I answer your question? Mark my post as a solution!