Rolling 4 weeks calculation

Hi Syndicate_Admin ,

See the below :

You data from 2020/1/1 to 2020/12/31,and week 1 from 2020/1/1 and end 2020/1/7

Try like following:

Table = CALENDAR("2020,1,1","2020,12,31")

weeknum = IF(YEAR('Table'[Date]-2)<2020,1, WEEKNUM('Table'[Date]-2,2))

get the below:

Due to without your detail data,I create a sample data:

Then  4 weeks rolls:

when week <=4 , get the sum that week < the actual number of weeks.

when week >4, get the sum that week >=actual number of weeks-3 and week <=actual number of weeks

roll4week = 
IF (
    MAX ( 'Table'[weeknum] ) <= 4,
    CALCULATE (
        SUM ( 'Table'[number] ),FILTER(ALL('Table'),
       'Table'[weeknum] <= max('Table'[weeknum] ))
    ),
    CALCULATE (
        SUM ( 'Table'[number] ),
        FILTER (
            ALL ( 'Table' ),
            'Table'[weeknum]
                >= MAX ( 'Table'[weeknum] ) - 3
                && 'Table'[weeknum] <= MAX ( 'Table'[weeknum] )
        )
    )
)

Wish it is helpful for you!

Best Regards

Lucien