Sum Rows with conditions

Hi rbeneteli,

Please check out the demo in the attachment. I believe you have a date table. The [Measure 2] is only for test purpose. 

Measure =
VAR lastMonthCode =
    CALCULATE ( MIN ( 'Table2'[bCODE] ), PREVIOUSMONTH ( 'Calendar'[Date] ) )
VAR last2Monthcode =
    CALCULATE (
        MIN ( 'Table2'[bCODE] ),
        DATESINPERIOD (
            'Calendar'[Date],
            EOMONTH ( MAX ( 'Calendar'[Date] ), -2 ),
            -1,
            MONTH
        )
    )
VAR last2MonthCodes =
    CALCULATETABLE (
        VALUES ( Table1[CODE] ),
        PREVIOUSMONTH ( 'Calendar'[Date] ),
        'Table1'[CODE] >= last2Monthcode
    )
RETURN
    CALCULATE (
        SUM ( Table1[VALUE] ),
        FILTER (
            'Table1',
            'Table1'[CODE] >= lastMonthCode
                || Table1[CODE] IN last2MonthCodes
        )
    )

Best Regards,
Dale