private void button1_Click(object sender, System.EventArgs e)
  {
   Excel.ApplicationClass excel=new Microsoft.Office.Interop.Excel.ApplicationClass ();
   excel.Application .Workbooks .Add (true);
   excel.Visible =true;
   Excel.Range myrange=excel.get_Range (excel.Cells [1,1],excel.Cells [2,2]);
   myrange.NumberFormatLocal ="@";
   excel.Cells [1,1]="0001";

  }