<?xml version="1.0" ?>

<mx:VBox xmlns:mx="http://www.adobe.com/2006/mxml">

    <mx:Script><![CDATA[

    public static final var value:Number=1;

        ]]></mx:Script>

    <mx:ComboBox>

        <mx:ArrayCollection>

            <mx:String>Dog</mx:String>

            <mx:String>Cat</mx:String>

        </mx:ArrayCollection>

    </mx:ComboBox>

</mx:VBox>

<mx:Script><![CDATA[

private function doSmth():void{

...

var n:Number = MyCombobox.value;

}

]]></mx:Script>