When the button is clicked, I want the file to be opened.
The file will be in the same directory as the visual basic project.
Therefore, I need the code to open the file using "app.Path".
And OPEN will open the text file, but not decode the XML inside of it.
The OPEN argument is not needed and you can also leave a blank string, because the ShellExecute has the open command as default one. See a guide on this API, that provided by AllAPI.net is a very good one.