MVC3 导出Excel 问题，急急急！！！！

1.后台从数据库取出数生成FileResult，正常情况下浏览器可直接导出excel了
但是现在想控制View层的按钮，点击导出按钮后禁用按钮，等事件完成再启用就出问题了。

后台代码：

  [HttpPost]

        public FileResult Index(ReportModel model)

        {

            if (!model.ReporType.HasValue)

            {

                return null;

            }



            byte reportTypeValue = 0;

            string reportName = string.Empty;

            ReportType accountMaster = _reportService.GetReportType(model.ReporType.Value);

            if (accountMaster == null)

            {

                return null;

            }

            else

            {

                reportTypeValue = accountMaster.Id;

                reportName = accountMaster.Name;

            }



            byte businessTypeValue = 0;

            string businessName = string.Empty;

            if (model.BusinessType.HasValue)

            {

                businessTypeValue = model.BusinessType.Value;

                businessName = _reportService.GetReportBusinessName(reportTypeValue, businessTypeValue);

            }



            var getUser = GetUser();

            ReportSearchCondition rsc = new ReportSearchCondition

            {

                ReportName = reportName,

                BusinessID = businessTypeValue,

                BusinessName = businessName,

                BeginTime = model.BeginTime.Value,

                EndTime = model.EndTime.Value.AddMilliseconds(997),

                OperaterID = getUser.UserCode,

                OperaterName = getUser.UserName

            };



            Func<ReportSearchCondition, DataSet> func = GetReportMethod(reportTypeValue);



            string fileName = string.Format("{0}从{1}到{2}",

                                                  rsc.BusinessID == 0 ? rsc.ReportName : rsc.BusinessName,

                                                  Convert.ToDateTime(rsc.BeginTime).ToString("yyMMdd"),

                                                  Convert.ToDateTime(rsc.EndTime).ToString("yyMMdd"));

            ExportDataToExcel(func, rsc);

            return File(fileName, "application/vnd.ms-excel");

        }

2.前台通过Ajax.BeginForm来异步控制，onbegin就执行startFunc脚本禁用导出按钮，onsuccess就
执行completeFunc启用导出按钮，但是这个时候，浏览器就不再出现下载EXCEL文件的提示了！！
整了一天，希望有高手指点。顺便说下Ajax.BeginForm 的 UpdateTargetId="Result" 能把报表结果导出到
id=result这个div下面展示到页面，就是TM不出现下载文件。
前台代码：

@model Myj.ELife.Financial.WebUI.Models.ReportModel

@{

    ViewBag.Title = "Index";

}



<div id="content">

    <fieldset>

        <legend>报表导出</legend>

        <div class="edit">

        @using (Ajax.BeginForm("Index", "Report", new AjaxOptions {

            LoadingElementId = "message",

       OnBegin = "startFunc",

       OnSuccess = "completeFunc" ,

       //UpdateTargetId="Result"

        }))

        {

            <table cellpadding="0" cellspacing="0" class="table_edit">

             <tr>

                <th>@Html.Encode("报表类型：")</th>

                <td>

                    @Html.DropDownList("ReporType", Model.AvailableReportTypeStatuses)

                </td>

                <th>@Html.Encode("业务类型：")</th>

               <td>

                @Html.DropDownList("BusinessType", Model.AvailableBusinessTypeStatuses)

               </td>

               </tr>

                <tr>

                    <th>

                        @Html.Encode("开始时间：")

                    </th>

                    <td> 

                        @Html.TextBox("BeginTime", null, new { @class = "mediumfield", @id = "txtBeginTime", onfocus = "WdatePicker({dateFmt:'yyyy-MM-dd HH:mm:ss',readOnly:true})" })

                    </td>

                

                    <th>

                        @Html.Encode("截止时间：")

                    </th>

                    <td> 

                        @Html.TextBox("EndTime", null, new { @class = "mediumfield", @id = "txtEndTime", onfocus = "WdatePicker({dateFmt:'yyyy-MM-dd HH:mm:ss',readOnly:true})" })

                    </td>

                </tr>

                 <tr>

                        <td colspan="4" style="text-align: center;">

                            <input class="button_big" type="submit" id="i_Export" value="报表导出" />

                        </td>

                    </tr>

                    <tr>

                        <td colspan="4" style="text-align: center;">

                            <div id="message" style="color: Red;display:none;">

                                 <img id="loadingImg" src="../../Content/themes/images/loadingData.gif" />正在导出...

                            </div>

                        </td>

                    </tr>

                     <tr>

                        <td colspan="4" style="text-align: center;">

                            <div id="Result" style="color: Red;">

                            </div>

                        </td>

                    </tr>

            </table>     

  

        }

        </div>

    </fieldset>

</div>

@*<script src="@Url.Content("../../Scripts/My97DatePicker/WdatePicker.js")" type="text/javascript"></script>*@

<script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script>

<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>

<script src="@Url.Content("~/Scripts/jquery.unobtrusive-ajax.min.js")" type="text/javascript"></script>



<script type="text/javascript">

    var startFunc = function () {

        $('input[id=i_Export]').attr('disabled', true);

        $('input[id=i_Export]').removeAttr('class');

    }

    var completeFunc = function () {

        $('input[id=i_Export]').removeAttr('disabled');

        $('input[id=i_Export]').attr('class', 'button_big');

        $.ajax({

                 type: this.method,

                  url:  this.action,

                  data:  $(this).serialize(),

                  });

    }

    $(document).ready(function () {



        $('select[id=ReporType]').change(function () {



            var id = $('select[id=ReporType]').val();

            //门店余额查询及深圳通明细查询（结算）不需要供应商

            if (id == 2 || id == 5) {

                $("#BusinessType").empty();

                $("<option></option>").val("").html("--请选择--").appendTo("#BusinessType");

                $('select[id=BusinessType]').attr("disabled", true);

                return false;

            }

            $('select[id=BusinessType]').attr("disabled", false);

            var url = '@Url.Content("~/Report/GetAccountDetails?id=")' + id + "&" + Math.random();

            $.getJSON(url, function (result) {

                $("#BusinessType").empty();

                $("<option></option>").val("").html("--请选择--").appendTo("#BusinessType");

                $.each(result, function (i) {

                    $("#BusinessType").append($("<option></option>").val(result[i].SupplierCode).html(result[i].SupplierName))

                });

            });

        });

      

        $('#i_Export').click(function () {

            var reporTypeId = $('select[id=ReporType]').val();

            if (typeof (reporTypeId) == undefined || reporTypeId == '') {

                alert("请选择报表类型");

                return false;

            }



            // 检查选择的业务类型，排除门店余额查询及深圳通明细查询（结算）

            if (reporTypeId != 2 && reporTypeId != 5) {

                var bussinessId = $('select[id=BusinessType]').val();

                if (typeof (bussinessId) == undefined || bussinessId == '') {

                    alert("请选择业务类型");

                    return false;

                }

            }



            //检查输入的日期是否合法

            var beginTime = $('#txtBeginTime').val();

            var endTime = $('#txtEndTime').val();



            if (typeof (beginTime) == undefined || beginTime == '') {

                alert("请输入开始时间！");

                return false;

            }



            if (typeof (endTime) == undefined || endTime == '') {

                alert("请输入结束时间！");

                return false;

            }



            var beginDate = new Date(beginTime.replace(/^(\d{4})(\d{2})(\d{2})$/, "$1/$2/$3"));

            var endDate = new Date(endTime.replace(/^(\d{4})(\d{2})(\d{2})$/, "$1/$2/$3"));



            if (beginDate > endDate) {

                alert("开始时间不能大于结束时间！");

                return false;

            }

        });

    })

</script>