[yorlin]

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical">
    <mx:Script>
        <![CDATA[
        	import mx.events.ListEvent;
        	private function clickTema(event:ListEvent):void
        	{
        		yourList.dataProvider = yourDataGrid.selectedItem.tema.@post;
        	}
       ]]>
    </mx:Script>
	<mx:DataGrid width="100%" itemClick="clickTema(event)" rowCount="2" id="yourDataGrid" dataProvider="{someXML.node}">
		<mx:columns>
			<mx:DataGridColumn dataField="tema" headerText="Tema"/>
		</mx:columns>
	</mx:DataGrid>
     <mx:XML id="someXML">
	    <nodes>
	   		<node>
	   			<tema post="df">tema1</tema>
	   		</node>
	   		<node>
	   			<tema post="da">tema2</tema>
	   		</node>
		</nodes>	
    </mx:XML>
 	<mx:List id="yourList" width="100" height="100"/>
</mx:Application>