Optimizing measure - Segment migration

Hi AlB ,

try this.

Net new customers v2 = 
VAR _CurrentDate =
    SELECTEDVALUE (Table1[Dates] )
VAR _PreviousDate =
    CALCULATE (
        MAX ( Table1[Dates] ),
        ALLSELECTED ( Table1[Dates] ),
        Table1[Dates] < _CurrentDate
    )
VAR _CountCustomerIDsThisMonth =
    CALCULATE( 
        DISTINCTCOUNT(Table1[CustomerId]),
        Table1[Dates] = _PreviousDate ||
        Table1[Dates] = _CurrentDate
    )
VAR _CountCustomerIDsPreviousMonth =
    CALCULATE( 
        DISTINCTCOUNT(Table1[CustomerId]),
        Table1[Dates] = _PreviousDate
    )
RETURN
    _CountCustomerIDsThisMonth - _CountCustomerIDsPreviousMonth