Sales-WTD =
VAR CD =
LASTDATE( 'Calendar'[Date] )
VAR CY =
MAX( 'Calendar'[Year] )
VAR WeekDayNo =
WEEKDAY( LASTDATE( 'Calendar'[Date] ), 3 )
RETURN
CALCULATE(
[Total Sales],
DATESBETWEEN(
'Calendar'[Date],
DATEADD(
CD,
-1 * WeekDayNo, DAY ),
CD),
'Calendar'[Year] = CY
)