A page called through server.execute has access to the Request object. Cookies, Application and Session variables, and any Form/Querystring variables passed to the page that contains the server.execute code is available to the called page.
I'd use session variable to pass info instead of the fso. The problem with writing variables to a specific file (not counting the file creation/io/deletion overhead) is that it can fall apart when you get multiple users with different variables writing to the same file. A session variable at least unique to a specific user.