% Chg vs LY =
DIVIDE (
    SUMX ( Sales, Sales[Qty] * Sales[Unit Price] )
        - CALCULATE (
            SUMX ( Sales, Sales[Qty] * Sales[Unit Price] ),
            SAMEPERIODLASTYEAR ( Calendar[Date] )
        ),
    CALCULATE (
        SUMX ( Sales, Sales[Qty] * Sales[Unit Price] ),
        SAMEPERIODLASTYEAR ( Calendar[Date] )
    )
)
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