导出网页形式的excel怎么设置单元格格式为自动换行???

Response.Clear();
            Response.Buffer = true;
            HttpContext.Current.Response.Charset = "UTF-8";
            HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.Default;
            HttpContext.Current.Response.ContentType = "application/vnd.ms-excel";
            HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" + "" + HttpUtility.UrlPathEncode("道路统计表" + DateTime.Now.ToString("yyyyMMddHHmmss")) + ".xls");
            this.Page.EnableViewState = false;
            System.IO.StringWriter oStringWriter = new System.IO.StringWriter();
            System.Web.UI.HtmlTextWriter oHtmlTextWriter = new System.Web.UI.HtmlTextWriter(oStringWriter);
            this.Page.RenderControl(oHtmlTextWriter);
            Response.Output.Write(oStringWriter.ToString());
            Response.Flush();
            Response.End();-----------------
我用web常用的方法导出成excel，页面gridview设置了宽度，每一列也设置了固定的宽度，可就是导出excel会变成一行，未自动换行，有没办法啊？