How do I add a change event for a custom attribute on a custom component?
Example code:

-----------------------------------------------------------

---- app.mxml ---
<mx:Applicationxmlns:mx="http://www.macromedia.com/2003/mxml" xmns:local="*">
<mx:DateChooser id="currentdate"/>
<local:MyComponent id="myComp" currentDate="{currentdate.currentDate}"/>
</mx:Application/>

--- MyComponent.mxml ---
<mx:Panel initialize="panelInit()"
xmlns:mx="http://www.macromedia.com/2003/mxml">
<mx:Date id="currentDate"/>
<mx:HTTPService url="myurl.php" id="myHTTPsrv">
<mx:request>
<date>{currentDate}</date>
</mx:request>
</mx:HTTPService>
<mx:Script>
<![CDATA[
function panelInit()
{
refresh();
}
function refresh()
{
myHTTPsrv.send();
}
]]>
</mx:Script>
<mx:List id="myList"
dataProvider="{mx.utils.ArrayUtils.toArray(myHTTPS rv.result.root.item}"/>
</mx:Panel >

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I want to trigger the refresh() function when the currentDate attribute to the
MyComponent panel is changed. Since it's bound to the DateChooser in the
app.mxml, it would fire everytime the DateChooser is changed.