onclick change the value of the text box

onclick change the value of the text box

Hi guys;

I use the code below to add or subtract the value of the text box of number of nights  in this link:

http://www.hotels2go.com.au/gallery_nd2.php?order=3&search_term=Gold+Coast&search_type=destination&search_id=18&id=53&altFormat=2013-05-03&checkin_term=3+May%2C+2013&nights=1&nights=1&nights=1&room_type=12&room_type_view=1+bedroom+apartment

This is my code and it doesnt work. It does call the funciton properly but doesnt update! Any ideas?

Thank you
  1. $(document).ready(function()
            {
               
    $(function()
    {
        $(".nights_minus").click(function()
        {
            var currentVal = parseInt($(this).next(".nights_text_box").val());
            if (currentVal != NaN)
            {
                $(this).next(".nights_text_box").val( Math.max(1,currentVal - 1) );
            }
        });

        $(".nights_plus").click(function()
        {
            var currentVal = parseInt($(this).prev(".nights_text_box").val());
            if (currentVal != NaN)
            {
                $(this).prev(".nights_text_box").val(currentVal + 1);
            }
        });
    });

    });