Does anyone know a script that would allow users to enter a file path and if the file extension ends in ".v2e" the file extension is changed to ".mp3" and the file is saved when they press a button, but if the file extension is anything other than ".v2e" an error message is shown?

And possibly it is a language like Javascript or DHTML rather than CGI or PHP, but PHP or CGI would do.
I know it's a tall order, but please if you can help me, please do!
