Get Layer By ComboBox

[weiwang3]

want to be able to turn on and off the layer (visibleLayers) by ComboBox. I'm attempting to create three ComboBoxs for the user to toggle the visibility of layers in a dynamic map service layer. these three ComboxBoxs Respectively represent "dynamic services", "Year", "Month" .
I know There are some mistakes the code , but I can not modify,Please help me.
I referred to the http://forums.arcgis.com/threads/2106-Radio-Button-on-off-Layers?highlight=Dynamic+layers

Here's One of them my relevant MapServer:

http://219.246.47.247/ArcGIS/rest/se...day5/MapServer


Service Description:

Map Name: Layers

All Layers and Tables

Layers:


xianjie (0)
ma021011 (1)
ma021021 (2)
ma031101 (3)
ma061215 (4)
ma061215 (5)

eg."ma021011": "ma" representative "Lable"; "02" representative "Year(2002)"; "10" representative "month"; "11" representative "day"

my relevant mxml:

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
xmlns:s="library://ns.adobe.com/flex/spark" 
xmlns:mx="library://ns.adobe.com/flex/mx" 
xmlns:esri="http://www.esri.com/2008/ags"
minWidth="955" minHeight="600">
<s:layout>
<s:VerticalLayout/>
</s:layout>
<fx:Script>
<![CDATA[
import mx.collections.ArrayCollection;
import mx.controls.RadioButton;
import mx.events.ItemClickEvent;

private function loadLayerName():void
{
layerPanel.removeAllChildren();

//loop through each layer and add as a radiobutton
var aa:String = "ma" + yearURL.selectedItem.toString() + monthURL.selectedItem.toString();


for(var i:uint = 0; i < (dynamicLayer.layerInfos.length); i++) 
{

if (aa = dynamicLayer.layerInfos.name);
{

var radioBtn:RadioButton = new RadioButton;
radioBtn.groupName = "radioBtnGroup";
radioBtn.value = i;
radioBtn.label = dynamicLayer.layerInfos.name;
layerPanel.addChild(radioBtn);
}
}

//set the visible layer the first radio button
radioBtnGroup.selectedValue = 0;
dynamicLayer.visibleLayers = new ArrayCollection([0]);
}

private function radioClickHandler(event:ItemClickEvent):void
{
// update the visible layers to only show the layer selected
dynamicLayer.visibleLayers = new ArrayCollection([event.index]);

} 
]]>
</fx:Script>
<fxeclarations>
<!--  -->
</fxeclarations>

<esri:Map id="myMap">

<esri:ArcGISDynamicMapServiceLayer id="dynamicLayer"
load="loadLayerName()"
url="http://219.246.47.247/ArcGIS/rest/services/{myURL.selectedItem}/MapServer" />
</esri:Map>

<mx:ComboBox id="myURL" selectedIndex="0" horizontalCenter="0">
<fx:Array>

<fx:String>day</fx:String>
<fx:String>day5</fx:String>
<fx:String>day10</fx:String>
</fx:Array>

</mx:ComboBox>

<mx:ComboBox id="yearURL">
<fx:Array>

<fx:String>2002</fx:String>
<fx:String>2003</fx:String>
<fx:String>2006</fx:String>
</fx:Array>

</mx:ComboBox>

<mx:ComboBox id="monthURL">
<fx:Array>

<fx:String>10</fx:String>
<fx:String>11</fx:String>
<fx:String>12</fx:String>
<fx:String>01</fx:String>
<fx:String>02</fx:String>
<fx:String>03</fx:String>
</fx:Array>

</mx:ComboBox>

<mx:Panel id="layerPanel" width="300" height="250" x="20" y="250" paddingLeft="20">
<mx:RadioButtonGroup id="radioBtnGroup" itemClick="radioClickHandler(event)"/>
</mx:Panel>

</s:Application>