【求助】 下载Word时的等待窗口? 无法触发js事件 。。。。

public partial class DownFile : System.Web.UI.Page

{

    protected void Page_Load(object sender, EventArgs e)

    {

        FileStream fileStream = new FileStream(Server.MapPath("readme.doc"), FileMode.Open);

        long fileSize = fileStream.Length;



        Response.ContentType = "application/octet-stream";

        Response.ContentType = "application/octet-stream";

        Response.AddHeader("Content-Disposition", "attachment; filename=\"" + HttpUtility.UrlEncode("readme.doc", System.Text.Encoding.UTF8) + "\"");

        Response.AddHeader("Content-Length", fileSize.ToString());

        byte[] fileBuffer = new byte[fileSize];

        fileStream.Read(fileBuffer, 0, (int)fileSize);

        fileStream.Close();

        Response.Write(fileBuffer);

        Response.End();

    }

}

----------------------------以上是下载页面。



<TABLE runat=server border="0" id="processBarMask" bgcolor="#cccccc" style="VISIBILITY:hidden; POSITION: absolute" cellspacing="0" cellpadding="0">
<TR>
等待中。。。。。。。。。。。。。。
</TR>
</TABLE>

<SCRIPT language="javaScript">

    var firstFlg = "0";



    function processStart(){

          with(document.all.processBarMask.style){

                 top = 0;

                 width = "100%";

                 height = "100%";

                 visibility = "visible";

          }

          document.all.processBarMask.focus();

    }



    function processEnd(){

        document.all.processBarMask.style.visibility = "hidden";

    }

</SCRIPT>

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下面有列表页中的一按钮，想执行一个文档转换，再提供下载，过程可能二三秒不定，看网络等多种因素。

protected void Button2_Click(object sender, EventArgs e)
{

// Response.Redirect("DownFile.aspx");
Page.ClientScript.RegisterStartupScript(Page.GetType(), "js", "<script language='javascript'>processEnd()</script>");
processBarMask.Style.Add("display", "none");
processBarMask.Visible = false;

}

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在调用下载页输出文件流后，服务器端却无法触发关闭等待table , 这个需求如何设计呢？？。。