我正在www.example.com中执行导出到excel的操作asp.net但没有使用任何第三方控件。如何为导出的excel工作表给予背景颜色？
背景颜色可能（不确定）根据一些单元格范围而不同。比如从单元格0- 5（excel中的单元格A-E）是红色，6-12是绿色等等。
我怎样才能达到同样的目的呢？

public static void DataSetToExcel(System.Data.DataSet dtExport, System.Web.HttpResponse response, string strFileName)
{
    //Clean up the response Object
    response.Clear();
    response.Charset = "";

    //Set the respomse MIME type to excel
    response.ContentType = "application/vnd.ms-excel";

    //Opens the attachment in new window
    response.AddHeader("Content-Disposition", "attachment; filename=" + strFileName.ToString() + ".xls;");
    response.ContentEncoding = Encoding.Unicode;
    response.BinaryWrite(Encoding.Unicode.GetPreamble());

    //Create a string writer
    System.IO.StringWriter stringWrite = new System.IO.StringWriter();

    //Create an htmltextwriter which uses the stringwriter
    System.Web.UI.HtmlTextWriter htmlWrite = new System.Web.UI.HtmlTextWriter(stringWrite);

    //Instantiate the datagrid

    System.Web.UI.WebControls.GridView dgrExport = new System.Web.UI.WebControls.GridView();

    //Set input datagrid to dataset table
    dgrExport.DataSource = dtExport.Tables[0];

    //bind the data with datagrid
    dgrExport.DataBind();

    //Make header text bold
    dgrExport.HeaderStyle.Font.Bold = true;

    //bind the modified datagrid
    dgrExport.DataBind();

    //Tell the datagrid to render itself to our htmltextwriter
    dgrExport.RenderControl(htmlWrite);

    //Output the HTML
    response.Write(stringWrite.ToString());

    response.End();
}