Function about Output Mapping in nwBPM

HI all

I am using PO 7.31 BPM, it receive request message with following structure ( note: this is sync process, I used BPM to return response message)

   Data structure:

         MT  -  Notification

         root        Event  1:1

                          EventList  0:N

                               field 1    0:1

                               field 2    0:1

                               EventCode

Event code could be:    "Power Failed", "Power Restored", "Over Voltage" etc.. there are over 10 other event code values.

After BPM  received the message, I need to filter out eventList with eventCode = "Power Failed" or "Power Restored", and ignore other types of events.

if there is no those two evenCode,

Similar to xslt syntax:

     <xsl:copy-of select="Notification/Event /EventList [EventCode='Power Failed' or EventCode='Power Restored']" />

I explored the function that BPM provided, it seems I could not find right function to achieve this.

Anyone has experience on this to share your thoughts ?

Thanks

-Liang