split value equally into months and cumulative

Thank you Ahmedx 

You solution is very close but for example PO 60800001452 should not have value in 2024 Jan and Feb.

I have managed to solve this problem by

1. Create a column to count the number of months between start and end date

Month Diff = DATEDIFF('BOH Hours'[Start],'BOH Hours'[End],month)+1

• Create a column to count the average hours per month 

AVG hours per month = DIVIDE('BOH Hours'[Contract Qty],'BOH Hours'[Month Diff])​

• Use the following Syntax (I found it in another post) to find the cumulative SUM in the range

Cumulative Contract Qty (within range) = 
VAR _s =
    SELECTEDVALUE( 'BOH Hours'[Start] )
VAR _e =
    SELECTEDVALUE( 'BOH Hours'[End] )
VAR _p =
    SELECTEDVALUE( 'BOH Hours'[PO] )
VAR _inrangeHours =
    CALCULATE(
        SUM( 'BOH Hours'[AVG hours per month] ),
        FILTER(
            ALL( 'BOH Hours' ),
            [PO] = _p
                && [Date] >= _s
                && [Date] <= _e
                && [Date] <= MAX( 'BOH Hours'[Date] )
        )
    )
VAR _notinrangeHours =
    CALCULATE(
        SUM( 'BOH Hours'[AVG hours per month] ),
        FILTER( ALL( 'BOH Hours' ), [Date] <= MAX( 'BOH Hours'[Date] ) )
    )
RETURN
    IF(
        _s = BLANK(),
        _notinrangeHours,
        IF( _e < MAX( 'BOH Hours'[Date] ), BLANK(), _inrangeHours )
    )

With the following result (Taken from my actual data so the PO number is different from sample)

you can write the final measure like this

Final = 
VAR _max = EOMONTH(CALCULATE(MAX('Data'[End date]),ALLEXCEPT(Data,Data[PO])),0)
VAR _Result = SUMX(
    SUMMARIZE('Data','Data'[PO],Data[Start date],Data[End date]),[cumulative])
RETURN IF(
MAX('Calendar'[Date])<=_max,_Result)

pls try this