Exporting datagrid to excel: Format cells?

Question

I'm exportin a datagrid to excel, but Excel file is without format colors cells border... Do you know how format it? thanks this is my code: Response.Clear(); Response.AddHeader("Content-Disposition", "attachment; filename=exportar.xls"); 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); dgNopaginado.Caption= ddPlanta.SelectedItem + ": "+ txtFechaIni.Fecha+"-"+txtFechaFin.Fecha; this.ClearControls(dgNopaginado); dgNopaginado.RenderControl(oHtmlTextWriter); Response.Write(oStringWriter.ToString()); Response.End();