[Javascript] Automatic Unique Form Numbering

[Jamesjackson73 at aol.com]

People
I have a form, but need to somehow generate an increasing UNIQUE number to be sent along with the form data. This could be whenever the form is loaded into the users browser or ideally when the user presses 'submit'. It would even be better if that number could become the 'subject' of the resulting email sent.
Hope someone knows how to help (Code even better).
Jim