Creating a tool tip on a Flex TextInput control with password masked text

<mx:TextInput id="ccNumber" text="4111111111111111" displayAsPassword="true" toolTip="{ccNumber.text}" /> <?xml version="1.0" encoding="utf-8"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" verticalAlign="middle" backgroundColor="white"> <mx:Script> <![CDATA[ import mx.formatters.DateBase; ]]> </mx:Script> <mx:Form> <mx:FormItem label="Name:"> <mx:TextInput id="ccName" text="JOHN DOE" /> </mx:FormItem> <mx:FormItem label="Number:"> <mx:TextInput id="ccNumber" text="4111111111111111" displayAsPassword="true" toolTip="{ccNumber.text}" /> </mx:FormItem> <mx:FormItem label="Type:"> <mx:ComboBox id="ccType" dataProvider="[American Express,MasterCard,Visa]" /> </mx:FormItem> <mx:FormItem label="Expiration:" direction="horizontal"> <mx:ComboBox id="ccExpMM" initialize="ccExpMM.dataProvider = DateBase.monthNamesShort;" /> <mx:ComboBox id="ccExpYYYY" dataProvider="[2008,2009,2010]" /> </mx:FormItem> </mx:Form> </mx:Application>