flex: duty enclosed component

this identical before posting. nonetheless i wish duty exists sure mxml page.

this sure mxml page:

main.mxml

<mx:application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" xmlns:ns1="*">
    <mx:script>
        <![cdata[   
        open duty changetext(currenttext:string):void{

            switch (currenttext){
                box "changetext":
                    lblone.text = "more text";                  
            }
        }
            ]]>
    </mx:script>

    <mx:hbox x="137.5" y="10" width="100%" height="100%">
        <ns1:menu id="buttons"> </ns1:menu>
    </mx:hbox>
    <mx:canvas x="137" y="88" width="408.5" height="200">
        <mx:hbox x="0" y="10" width="388.5" height="190">
            <mx:panel width="388" height="179" layout="absolute">
                <mx:label x="10" y="10" text="some text" visible="{buttons.showlabel}" id="lblone"/>
            </mx:panel>
        </mx:hbox>
    </mx:canvas>
</mx:application> 

here enclosed page:

menu.mxml

<?xml version="1.0" encoding="utf-8"?>
<mx:canvas xmlns:mx="http://www.adobe.com/2006/mxml" width="400" height="300">
    <mx:script>
        <![cdata[
            [bindable] open var showlabel:boolean = true;
        ]]>
    </mx:script>
    <mx:menubar width="380" height="58"></mx:menubar>
    <mx:button x="10" y="10" width="80" label="show" id="btnone" click="this.showlabel=true;" />
    <mx:button x="94" y="10" width="80" label="hide" id="btntwo" click="this.showlabel=false;"/>
    <mx:button x="181" y="10" width="80" label="run function" id="btnthree" click="{changetext('changetext')}"/>
</mx:canvas>

how i changetext duty symbol menu.mxml?