如何在Delphi应用程序中创建虚拟文件

I had a previous post on how to make memorystream play in wmp activex and got a reply with a link to boxedapp sdk. It's not a freeware so I studied the process and I figured out that it is using a virtual file for the stream to be saved and that its filename is used as the URL. So, my question is how to create a virtual file that returns a handle which should be then be accessed by a THandleStream. I am using Delphi 7. Thanks. on how to make memorystre