private ReceiptAcknowledgementMsg getAck(Segment segment )
        {
            var els = segment.GetElements(_elementDelimiter);
            var ack = new ReceiptAcknowledgementMsg();
            ack.ControlNumber = els[2];
            ack.DocumentId = els[1].CastToInt();

            return ack;
        }
        private ReceiptAcknowledgement getAck(ReceiptAcknowledgementMsg ackMsg, Acknowledgements acks)
        {
            var ack = GetSentDocument(ackMsg.ControlNumber.CastToInt());
                                      if(ack == null)
                                          throw new EDIWorkflowException(
                                              string.Format(
                                                  "The ACK placeholder for control number {0} was not found!",
                                                  ackMsg.ControlNumber));
            ack.AckReceiveDate = DateTime.Now;
            ack.AckControlNumber = acks.ControlNumber.CastToInt();

            return ack;
        }