<form id="frmbox" method="post" action="/ajaxaction.php"></form>

function AjaxSubmit() {
            var ajax = new AJAXRequest();
            ajax.postf("frmbox", Callback);
        }
function Callback(obj) //回调函数,显示结果
        {
            var a = obj.responseText;
            result = 0;
            if (!isNaN(a))    result = parseInt(a);
        }