Variables in Adobe Flex

I'm tyring to use a variable that I declare in my CDATA later on in my flex document. How can I manipulate "userid" in the CDATA and also send it off in the later HTTPService code?

<fx:Style source="felxible_1.css"/>

<fx:Script>
    <![CDATA[
        public var userid:String;
    ]]>
</fx:Script>

<fx:Declarations>


    <mx:HTTPService         
        id="fetch_list_1"           
        result="listfetched1(event)"开发者_C百科
        method="POST"           
        url="find_data_1.php"
        useProxy="false">
        <mx:request xmlns="">
            <userid>userid</userid>
        </mx:request>
    </mx:HTTPService>

</fx:Declarations>

You need to use the "binding" syntax. In your script, make the variable send update messages when you change it:

[Bindable] var userid:String;

Then, in the markup, tell the userid tag to update when the variable changes.

<userid>{userid}</userid>