Export Gridview to Excel, too much info

I am using the following code to export a gridview into Excel:

                Response.Clear();
                Response.AddHeader("content-disposition", "attachment;filename=Alldata.xls");
                Response.Charset = "";
                Response.Cache.SetCacheability(HttpCacheability.NoCache);
                Response.ContentType = "application/vnd.ms-excel";
                System.IO.StringWriter stringWrite = new System.IO.StringWriter();
                System.Web.UI.HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);
                GridView1.RenderControl(htmlWrite);
                Response.Write(stringWrite.ToString());
                Response.End();

On the same form that the gridview control is in there is also a couple of  dropdown list with various information.  Well when I use the above code to export the Gridview I get all the values from the dropdowns to appear on the spreadsheet too.  How do I make it so only the information from the gridview appears in the Excel spreadsheet and nothing else? Thanks.