How to set message label using Weborb(Producer) and MSMQ

I`m adding a message in MSMQ by my flex program using this code:

            producer = new Producer();
            producer.destination = "VendingMachineBack";
            var m:AsyncMessage = new AsyncMessage("",{'MSMQLabel':"VS-GetSaleTypes"}) ;
            producer.send(m);   

and my weborb messaging-config.xml it`s the following:

<destination channels="weborb-rtmp" id="VendingMachineBack">
    <properties>
      <msmq>
        <path>.\private$\ClassicBackEndQueue</path>
        <deliverPastMessages>-1</deliverPastMessages>
        <BasePriority>0</BasePriority>
        <Category>00000000-0000-0000-0000-000000000000</Category>
        <MaximumQueueSize>4294967295</MaximumQueueSize>
        <UseJournalQueue>false</UseJournalQueue>
        <MaximumJournalSize>4294967295</MaximumJournalSize>         
      </msmq>
    <message-service-handler>Weborb.Messaging.PubSub.Msmq.MessagingServiceHandler</message-service-handler>
    </properties>
    <channels>
        <channel ref="weborb-rtmp"/>
    </channels>
</destination>  

The thing is, how can I set the message label in the AsyncMessage that I`m sending?

I found the solution after while! there is no why to set a message label using webOrb, so I just migrate to FluorineFX: http://www.fluorinefx.com/ and then I did it: http://www.fluorinefx.com/docs/fluorine/messagingmsmq.html