Change file's name when it's uploaded via html form

Hi everyone!

Is there any way to change the filename when it's uploaded via html form?

I understand that I need a form like this:

<form id="upload_form" method="post" enctype="multipart/form-data">
    <input type="file" name="upload_file">
    <input type="submit">
  </form>

And in my Javascript this:

$('#upload_form').attr('action', everlive.files.getUploadUrl());

Then, the file will be uploaded with its original name... but I want to add some characters at the end of the filename... is there any way to change the name when I upload files by this way?

Thank you and sorry for my english.