Take a look at http://fox.wikis.com/wc.dll?Wiki~DDE.

>I have an application compiled into an exe. I have added a file extension association to windows for *.flt to run this application and pass the file name to the application which then proceeds to load and display that document in a window within the app. Everything works fine except when the application is already loaded, it loads again and displays the document in another instance of the program. How can I have the currently running instance simply bring up the document in itself instead of loading another instance? I think it would have to start loading a new instance, then determine if it is already running (how, I'm not sure), then, if it is, pass the file name reference to the running instance and shut itself down. How could this be accomplished?
>Thanks.