[flexcoders] Flex Webservices

[flexnewbie06]

Hi group.

I'm using flex data services (sdk 2.0) and wondering if anyone has ever tried 
to set up operation parameters pro grammatically?  I can't seem to figure out 
how one would do so without specifically binding to some variable.

for example here is the service operation.

                <mx:operation name="removeDVRRecording" 
fault="showFault(event);showError(event)">
                    <mx:request>                        
                 <RemoveRequest accountExternalId="{accountVuExtId}">           
    
                     <RemoveRecording>
                      <!--Zero or more repetitions:-->
                       <recording recordingEventId="{accountVuRemRecordings}"/>
                    </RemoveRecording>
                </RemoveRequest>
                    </mx:request>
                </mx:operation>

Is it possible to append elements into the children of the service?  Or maybe 
there is a better approach.

Suggestions Greatly appreciated
Jenn