AS3 xml帮助：更新并保存xml文件

i am working with adobe flash cs6 with as3. i have a XML file and i needed to add a node to it .when i tried its working fine.but when the instance is closed,i opened the XML file with notepad ,it doesn't actually saved to original file.my XML file is stored locally in the same folder of flash project. I need a solution without using other languages like PHP. please helpi am working with adobe flash cs6 with as3. i h