Flex Datagrid pagination

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" creationComplete="InitApp()" xmlns:MyComp="*">
<mx:Script>
	<![CDATA[
		import mx.collections.ArrayCollection;
		import mx.events.ItemClickEvent;
		[Bindable]
		public var myData:ArrayCollection = new ArrayCollection();
		public var orgData:ArrayCollection = new ArrayCollection();
		[Bindable]
		public var nav:ArrayCollection = new ArrayCollection();
		private var index:int = 0;
		private var page:int = 25;		
		private var paging:Boolean = true;
		
		private function InitApp():void {
			for( var x:uint = 1; x <= 500; x++ ) {
				var obj:Object = new Object();
				obj.Id = x.toString();
				obj.Name = "Column " + x.toString();
				obj.Street = "5555 Street";
				obj.Title = "CEO";
				obj.City = "El Paso";
				orgData.addItem(obj);
			}
			refreshDataProvider(0);
		}
 
		private function navPage(d:int):void {
			index += d;
			refreshDataProvider(index);	
		}
		
		private function refreshDataProvider(start:int):void {
			if (paging == true) {
				page = 25;
				myData = new ArrayCollection(orgData.source.slice(start,start+page));
			}
			else {
			index = 0;
				page = 500;
				myData = new ArrayCollection(orgData.source);				
			}
			down.enabled = index > 0;
			up.enabled = index + page < orgData.length;
			lbl.text = index.toString() + ' to ' + (index + page).toString() + ' of ' + orgData.length;   			
		}
		
		private function togglePaging():void {
			paging = !paging;
			toggle.label = paging.toString();
			refreshDataProvider(index);
		}
 
]]>
</mx:Script>
	<mx:DataGrid id="dg" dataProvider="{myData}" width="510" height="202"></mx:DataGrid>
	<mx:Button x="10" y="210" label="&lt;" click="navPage(-25);" id="down"/>
	<mx:Button x="216" y="210" label="&gt;" click="navPage(25);" id="up"/>
	<mx:Label x="58" y="212" text="page" width="150" id="lbl"/>
	<mx:Button x="264" y="210" label="true" id="toggle" click="togglePaging();"/>
 
</mx:Application>
                                              

1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:
32:
33:
34:
35:
36:
37:
38:
39:
40:
41:
42:
43:
44:
45:
46:
47:
48:
49:
50:
51:
52:
53:
54:
55:
56:
57:
58:
59:
60:
61:
62:
63: