excel的问题

[jackljane]

我导出的excel是用rendercontrol()方法导出的。
但是现在要求在导出之前把一个图片也插入到要导出的excel中去。如何做？不想用application.有没有其它的办法。附我的导出方法。

Response.ContentType = "application/vnd.ms-excel";
Response.Charset = "UTF-8";
Response.AppendHeader("Content-disposition", "attachment;filename = Monthly.xls");
System.IO.StringWriter SISW = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter SWUHTW = new HtmlTextWriter(SISW);
Page.RenderControl(SWUHTW);

//想在此处把图片插入到Monthly.xls中.

Response.Write(SISW);
Response.End();