Calculate record within selected dataset

Hi,

I am using the following formula in my measure to count number of Sales Document that have been processed per month:

# Sales Document Rolling =

    CALCULATE(

        SalesTable[# Sales Document Processed],

        DATESINPERIOD(

            DateTable[Date],

            MAX(DateTable[Date]),

            -1,

            MONTH

       ),

       USERELATIONSHIP(

            SalesTable[DocumentProcessedDate], DateTable[Date]

        )

    )

This return the correct result; it gives me the number of Sales Document that have been processed in the selection month (using Document Processed Date).

However, how can I include another condition here to filter only those Sales Document that are created in the selected month?

I have Document Created Date in my SalesTable.  So, it should be:

1. Select all the Sales Document created in the selected month (using Document Created Date).
2. Then calculated how many Sales Document have been processed (using DocumentProcessedDate).

Please help.

Thank you.