Taking Distinct count after calculating a measure

hi Anonymous9999 

try to create plot a table visual with the measure like this:

Result = 
VAR CurrentMonth = MONTH(MAX(TableName[Joining Date]))
RETURN
CALCULATE(
    DISTINCTCOUNT(TableName[Teacher]),
    FILTER(
        ALL(TableName),
        MONTH(TableName[Joining Date])<=CurrentMonth            
    )
) -
CALCULATE(
    DISTINCTCOUNT(TableName[Teacher]),
    FILTER(
        ALL(TableName),
        OR (
            AND ( 
                MONTH(TableName[Terminated Date])<>BLANK(), 
                MONTH(TableName[Terminated Date])=CurrentMonth
            ),
            AND( 
                MONTH(TableName[Graduated Date])<>BLANK(), 
                MONTH(TableName[Graduated Date])=CurrentMonth
            )
        )
    )
)

i tried and it worked like this:

the dataset: