Calculate miles driven

Question

Trying to calculate miles driven:

Mileage Driven = IF(

    ISFILTERED('Mileage Tracker'[Month]),

    ERROR("Time intelligence quick measures can only be grouped or filtered by the Power BI-provided date hierarchy or primary date column."),

    VAR __PREV_MONTH =

        CALCULATE(

            SUM('Mileage Tracker'[Odometer Reading]),

            DATEADD('Mileage Tracker'[Month].[Date], -1, MONTH)

        )

    RETURN

        Divide(

            SUM('Mileage Tracker'[Odometer Reading]) - __PREV_MONTH,

            __PREV_MONTH

        )

)