Event handler for a text field

Question

How do I write an event handler that will be triggered when the value of a text field changes? I assume I can place an event in place of SOME EVENT HERE in the example below.
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
    <mx:Script>
        <![CDATA[
            private var newVal:Number=1
            public function doThis():void{
                newVal+=1
                goal1.text=String(newVal)
                //goal1.addEventListener(SOME EVENT HERE, textChange)
            public function textChange():void{
                trace("text changed")
        ]]>
    </mx:Script>
    <mx:Text id="goal1" color="#57782f" fontSize="30" text="1"  x="106" y="110"/>
    <mx:Button x="88" y="169" label="Button" click="doThis()"/>
</mx:Application>

Answer 1

"Text" does not dispathc a change event, so use a TextArea tweaked as follows.
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<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
    <mx:Script>
        <![CDATA[           
            private var newVal:Number=1
            public function doThis():void{
                newVal+=1
                goal1.text=String(newVal)
                goal1.addEventListener(Event.CHANGE, textChange)
            public function textChange():void{
                trace("text changed")
        ]]>
    </mx:Script>
    <mx:TextArea id="goal1" color="#57782f" fontSize="30" text="1"  x="106" y="110"
     focusThickness="0" borderThickness="0" backgroundAlpha="0"/>
    <mx:Button x="88" y="169" label="Button" click="doThis()"/>
</mx:Application>