You cannot retrieve the path of the submitted file server side, it is
simply not possible - browsers will not share that information with
you, neither via HTTP requests, nor by poking at the DOM with
javascript.
If it is absolutely necessary, you must provide a second text input
and have the user manually put the information in there. Bear in mind
that there would be no way of verifying that what the user put in that
box is at all correct.
Can you explain what you are trying to do rather than what is going
wrong, because I think that would be illuminating.
Cheers
Tom