Gravity Forms coupon code - jQuery

<script type="text/javascript">
$(document).ready(function(){

    //  when enter coupon code text, update the coupon amount field accordingly
    // 'Allow field to by dynamically populated' must be checked in form field editor
    //  to allow for negative values. no parameters needed.
    $('#input_3_18').bind("input",function(){

        var form_id    = 3;              // which form
        var field_id   = 17;             // coupon AMOUNT field
        var coupon     = $(this).val();  // coupon text code field value
        var minlength  = 4;              // minimum length of coupon code before start checking
        var ajaxpath   = 'http://www.yoursite/wp-admin/admin-ajax.php';
        var adminLabel = 'coupon_codes';

        if(coupon.length > minlength){

            // clear the value of the coupon amount
            $("#ginput_base_price_"+form_id+"_"+field_id).val(0);
            $("span#input_"+form_id+"_"+field_id).html("-$0.00");

            // update the form total price
            gformCalculateTotalPrice(form_id);

            // indicate that the form is thinking
            $(".ginput_total").append('<span id="loading"> ...validating</span>');

            fieldchoices = '';
            // retrieve a list of valid coupon codes, ajax function in functions.php
            $.ajax({
                url:ajaxpath,
                type:'POST',
                data:'action=getchoices_fromfield&adminLabel='+adminLabel+'&form_id='+form_id,
                success: function(results) {
                    // get an array of choices
                    fieldchoices = $.parseJSON(results);

                    $.each(fieldchoices, function(index, obj) {
                        // case insensitive comparison of entered code and valid codes
                        if(coupon.toLowerCase() == obj.text.toLowerCase()){
                            // update the coupon amount input field
                            $("#ginput_base_price_"+form_id+"_"+field_id).val(-obj.value);
                            $("span#input_"+form_id+"_"+field_id).html('-$'+obj.value);
                            // update the form total
                            gformCalculateTotalPrice(form_id);
                        }
                    });
                }
            });
            $("#loading").fadeOut(5000);
        }
    });
});
</script>