Help with DAX code

OK, the failure here was that your sample data was not representative of your actual data. In your actual data, we have to account for Employee_ID. So, that can be done like this:

Result = 
    VAR __CalculatedPay = 'Sheet1'[Calculated Pay (N)]
    VAR __Next = 
        MINX(
            FILTER(
                'Sheet1',
                'Sheet1'[Calculation Date] > EARLIER('Sheet1'[Calculation Date]) &&
                    'Sheet1'[Employee_ID] = EARLIER('Sheet1'[Employee_ID])
            ),
            'Sheet1'[Calculation Date]
        )
    VAR __NextPay = 
        MINX(
            FILTER(
                'Sheet1',
                'Sheet1'[Calculation Date] = __Next &&
                    'Sheet1'[Employee_ID] = EARLIER('Sheet1'[Employee_ID])
            ),
            'Sheet1'[Calculated Pay (N)]
        )
RETURN
    IF(__CalculatedPay <> __NextPay,__CalculatedPay,0)

Updated PBIX is attached.