Not sure particular sheet means. But, I've the code to export GridView data into excel as:
private void ExportToExcel(string strFileName, GridView dg)
{
Response.Clear();
Response.Buffer = true;
Response.ContentType = "application/vnd.ms-excel";
Response.Charset = "";
this.EnableViewState = false;
System.IO.StringWriter oStringWriter = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter oHtmlTextWriter = new System.Web.UI.HtmlTextWriter(oStringWriter);
oHtmlTextWriter.WriteLine("<font size="5"><font color="blue"><center> REPORT </center></font></font>");
GridView1.RenderControl(oHtmlTextWriter);
Response.End();
}