Cumulative data in Dax

Hi,

I am not sure if I understood your question correctly, but please check the below picture and the attached pbix file.

Planned start date count: =
IF (
    MIN ( 'Calendar'[Date] ) + 7
        >= MIN ( Data[Planned Start Date] )
        && MAX ( 'Calendar'[Date] ) - 7
            <= MAX ( Data[Planned End Date] ),
    CALCULATE (
        COUNTROWS (
            FILTER (
                Data,
                Data[Planned Start Date] <= MAX ( 'Calendar'[Date] )
                    && Data[Planned Start Date] >= MIN ( 'Calendar'[Date] )
            )
        ),
        WINDOW (
            1,
            ABS,
            0,
            REL,
            ALL ( 'Calendar'[WK enddate] ),
            ORDERBY ( 'Calendar'[WK enddate], ASC )
        )
    )
)

Planned end date count: = 
IF (
    MIN ( 'Calendar'[Date] ) + 7
        >= MIN ( Data[Planned Start Date] )
        && MAX ( 'Calendar'[Date] ) - 7
            <= MAX ( Data[Planned End Date] ),
    CALCULATE (
        COUNTROWS (
            FILTER (
                Data,
                Data[Planned End Date] <= MAX ( 'Calendar'[Date] )
                    && Data[Planned End Date] >= MIN ( 'Calendar'[Date] )
            )
        ),
        WINDOW (
            1,
            ABS,
            0,
            REL,
            ALL ( 'Calendar'[WK enddate] ),
            ORDERBY ( 'Calendar'[WK enddate], ASC )
        )
    )
)