<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/06/19/enabling-and-disabling-radiobutton-controls-in-a-radiobuttongroup-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            private function checkBox_change(evt:Event):void {
                radioGroup.enabled = checkBox.selected;
            }
        ]]>
    </mx:Script>

    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain">
            <mx:FormItem label="enabled:">
                <mx:CheckBox id="checkBox"
                        selected="true"
                        change="checkBox_change(event);" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>

    <mx:RadioButtonGroup id="radioGroup" />

    <mx:VBox horizontalAlign="left">
        <mx:RadioButton id="radioButton1"
                label="Red"
                group="{radioGroup}" />
        <mx:RadioButton id="radioButton2"
                label="Orange"
                group="{radioGroup}" />
        <mx:RadioButton id="radioButton3"
                label="Yellow"
                group="{radioGroup}" />
        <mx:RadioButton id="radioButton4"
                label="Green"
                group="{radioGroup}" />
        <mx:RadioButton id="radioButton5"
                label="Blue"
                group="{radioGroup}" />
    </mx:VBox>

</mx:Application>