each function 有关问题

each function 问题
享用 jquery 实现一下下面功能 ， 购物车自动计算金额表单 网上有提供， 我想增加个输入框，基本思路是，输入数字，下面商品数量都跟着变，而且后面对应的总价也跟着变。。。 

$(".num-pallets-input").each(function() 这个无法判断 同行内价格数值 ，如何实现 》？

JScript code

function IsNumeric(sText){   var ValidChars = "0123456789.";   var IsNumber=true;   var Char;    for (i = 0; i < sText.length && IsNumber == true; i++)       {       Char = sText.charAt(i);       if (ValidChars.indexOf(Char) == -1)          {         IsNumber = false;         }      }   return IsNumber;   };function calcDiscount() {        var DRate = $(".changediscount").val() || 0;    $(".num-pallets-input").each(function(){           $(".num-pallets-input").val(DRate);                        });            };function calcProdSubTotal() {        var prodSubTotal = 0;    $(".row-total-input").each(function(){            var valString = $(this).val() || 0;                prodSubTotal += parseInt(valString);                        });            $("#product-subtotal").val(prodSubTotal);};function calcTotalPallets() {    var totalPallets = 0;    $(".num-pallets-input").each(function() {            var thisValue = $(this).val();            if ( (IsNumeric(thisValue)) &&  (thisValue != '') ) {                    totalPallets += parseInt(thisValue);                };        });        $("#total-pallets-input").val(totalPallets);};function calcShippingTotal() {    var totalPallets = $("#total-pallets-input").val() || 0;    var shippingRate = $("#shipping-rate").text() || 0;    var shippingTotal = totalPallets * shippingRate;        $("#shipping-subtotal").val(shippingTotal);};function calcOrderTotal() {    var orderTotal = 0;    var productSubtotal = $("#product-subtotal").val() || 0;    var shippingSubtotal = $("#shipping-subtotal").val() || 0;            var orderTotal = parseInt(productSubtotal) + parseInt(shippingSubtotal);    var orderTotalNice = "$" + orderTotal;        $("#order-total").val(orderTotalNice);        };$(function(){     $('.changediscount').blur(function(){                   calcDiscount();             });    $('.num-pallets-input').blur(function(){            var $this = $(this);            var numPallets = $this.val();        var multiplier = $this                            .parent().parent()                            .find("td.price-per-pallet span")                            .text();                if ( (IsNumeric(numPallets)) && (numPallets != '') ) {                        var rowTotal = numPallets * multiplier;                        $this                .css("background-color", "white")                .parent().parent()                .find("td.row-total input")                .val(rowTotal);                                        } else {                    $this.css("background-color", "#ffdcdc");                                 };                calcProdSubTotal();        calcTotalPallets();        calcShippingTotal();        calcOrderTotal();        });});

JScript code

function calcDiscount() {        var DRate = $(".changediscount").val() || 0;    $(".num-pallets-input").each(function(){          this.val(DRate);//改为this      //计算金额，赋值等                  });};