Month End Value and Current Date Value

Here is a measure that should work in a table visual with your Date column from the table you've shown.  I called it targets, so change it to your actual table name.  This assumes you are using your Date table for the slicer but that there is no relationship to the targets table. 

Tgt =
VAR vDateValue =
    MIN ( 'Date'[Date] )
VAR vTgtMonthDate =
    MIN ( Targets[Date] )
VAR vWkDays =
    FILTER (
        CALENDAR (
            DATE ( YEAR ( vTgtMonthDate ), MONTH ( vTgtMonthDate ), 1 ),
            EOMONTH (
                vTgtMonthDate,
                0
            )
        ),
        WEEKDAY ( [Date] )
            IN {
            2,
            3,
            4,
            5,
            6
        }
    )
VAR vWkDaysPast =
    FILTER (
        vWkDays,
        [Date] <= vDateValue
    )
VAR vMonthTgt =
    MIN ( Targets[ Amount ] )
RETURN
    DIVIDE (
        COUNTROWS ( vWkDaysPast ) * vMonthTgt,
        COUNTROWS ( vWkDays )
    )

Regards,

Pat

Since you have a relationship between Dates and DT, please try this instead.  If it doesn't work, please send a link to your pbix (or a mock up of it), and I can get it working on this end.

Tgt = 
VAR vDateValue =
    MIN ( Dates[Date] )
VAR vTgtMonthDate =
    CALCULATE( MIN( DT[Date] ), ALL( Dates ), VALUES( DT[Date]))
VAR vWkDays =
    FILTER (
        CALENDAR (
            DATE ( YEAR ( vTgtMonthDate ), MONTH ( vTgtMonthDate ), 1 ),
            EOMONTH (
                vTgtMonthDate,
                0
            )
        ),
        WEEKDAY ( [Date] )
            IN {
            2,
            3,
            4,
            5,
            6
        }
    )
VAR vWkDaysPast =
    FILTER (
        vWkDays,
        [Date] <= vDateValue
    )
VAR vMonthTgt =
    CALCULATE( MIN ( DT[Amount] ), ALL(Dates), VALUES(DT[Date]))
RETURN
    DIVIDE (
        COUNTROWS ( vWkDaysPast ) * vMonthTgt,
        COUNTROWS ( vWkDays )
    )

Regards,

Pat

I saw same behavior with CALENDAR, so went another way.  Please try this expression instead.  Let me know if it works or if any questions on what it's doing.  This seems to work in a table visual with your Target[Date].

Target to Selected Date =
VAR vDateValue =
    MIN ( Dates[Date] )
VAR vTgtMonthDate =
    CALCULATE (
        MIN ( Target[Date] ),
        ALL ( Dates )
    )
VAR vTgtMonthStart =
    DATE ( YEAR ( vTgtMonthDate ), MONTH ( vTgtMonthDate ), 1 )
VAR vEndDate =
    IF (
        vTgtMonthDate < vDateValue,
        vTgtMonthDate,
        vDateValue
    )
VAR vWkDaysPast =
    CALCULATE (
        SUM ( Dates[Working Day] ),
        FILTER (
            ALL ( Dates[Date] ),
            Dates[Date] >= vTgtMonthStart
                && Dates[Date] <= vEndDate
        )
    )
VAR vWkDays =
    CALCULATE (
        SUM ( Dates[Working Day] ),
        FILTER (
            ALL ( Dates[Date] ),
            Dates[Date] >= vTgtMonthStart
                && Dates[Date] <= vTgtMonthDate
        )
    )
VAR vMonthTgt =
    CALCULATE (
        SUM ( Target[Amount] ),
        ALL ( Dates )
    )
VAR result =
    DIVIDE (
        vWkDaysPast * vMonthTgt,
        vWkDays
    )
RETURN
    result

I used a date slicer on Dates[Date] and used the min value in the expression.  Not sure how you are selected the date.

Regards,

Pat

I did use your pbix but it did not have any visuals, so I couldn't see how you were selecting the date.  Here is my file.

Regards,

Pat