How to monitor the itemClick in FlexRadioButtonGroup when RadioButton was clicked

How to monitor the itemClick in FlexRadioButtonGroup when RadioButton was clicked

The full codes:
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layout=”vertical”
verticalAlign=”middle”
backgroundColor=”white” viewSourceURL=”srcview/index.html”>

private function radioGroup_itemClick(evt:ItemClickEvent):void {
var now:String = new Date().toTimeString();
lbl.text = evt.label + ” (” + now + “)”;
}
]]>
itemClick=”radioGroup_itemClick(event);” />
label=”Red”
group=”{radioGroup}” />
label=”Orange”
group=”{radioGroup}” />
label=”Yellow”
group=”{radioGroup}” />
label=”Green”
group=”{radioGroup}” />
label=”Blue”
group=”{radioGroup}” />