You'd have to open your computer up to the internet, and call the requested file over http.
However, if your computer at home goes down, is restarting, or changes IP, or your ISP goes down, then you'll have to make the adjustments to the script and could cause more problems than it's worth. Depends on how important that file is to your site.
Why don't you just upload the file to the webhost and host it there???