How to Set Delivery status Automatically...

Hello Experts ,

    I Wanna know about the Proof of Delivery and how the status of delivery is set to Confirmed(From Status A to C) Automatically. Also How this 'WS_DELIVERY_UPDATE_2' Standard Bapi works .

     To Raise an Invoice for a Delivered item the status of the Goods should be Converted to Confirmed state. Then Only we can raise the Invoice. So Do we have any table-fields which stores the automatic confirmation of the delivery status or Do we need to do anything manually .

                                 Thanks in Advance....

Rewarded if really helpful.