Just use change() handler for input type file, not keyup:

http://jsfiddle.net/nA37d/169/

 $("input[name='a1']").change(function() {
        $("input[name='b1']").val($(this).val());
    });

For input file to input file, i dont think its possible for security reason.

BTW, this code should be refactorized.