Passing a parameter to HttpService in Flexbuilder 3

I have stuck at the point where i need to pass a selected item of a comboBox as a paramet开发者_高级运维er to a HttpService.Can someone tell me how to do this.

Try the following code below

params["serviceParamName"] = comboBox.selectedItem;
httpServ.send(params);

<mx:HTTPService id="httpServ">
    <mx:resultFormat>flashvars</mx:resultFormat>
    <mx:url>http://www.adobe.com</mx:url>
    <mx:result>combo.selectedItem=httpServ.lastResult.message</mx:result>
    <mx:fault>Alert.show(event.toString(), event.type);</mx:fault>
</mx:HTTPService>