IIRC, you'll be getting a value of a temp file from your http server... you can use any sort of data to move that file from the temp directory to whatever your script decides.
So, any form data sent in the same form that uploads the file should be easily accessed.
BTW, the way you mention 3 HIDDEN VARIABLE VALUES, makes me terribly worried that you might think of using the values as some sort of security measure, which is not any sort of security at all... all hidden values are visible in the source code, and sent in cleartext over internet connections. If this is not the case, my apologies, and please disregard this last paragraph.
