Create a Column in Matrix which does (this week price) - (last week price) for multiple weeks

Hi JACK__ ,

According to your description, here are my steps you can follow as a solution.

(1) This is my test data. 

(2) We can create a calculated column.

Change = 
IF (
    [Week]
        = CALCULATE (
            MIN ( 'Table'[Week] ),
            FILTER ( ALL ( 'Table' ), 'Table'[Item] = EARLIER ( 'Table'[Item] ) )
        ),
    BLANK (),
    [Price]
        - CALCULATE (
            SUM ( 'Table'[Price] ),
            FILTER (
                'Table',
                'Table'[Item] = EARLIER ( 'Table'[Item] )
                    && 'Table'[Week]
                        = EARLIER ( 'Table'[Week] ) - 1
            )
        )
)

(3) Then the result is as follows.

Best Regards,

Neeko Tang

If this post  helps, then please consider Accept it as the solution  to help the other members find it more quickly.