protected void BtnChk_Click(object sender, EventArgs e)
{
    Process.Start(@"\servervol1FilesBook1.xls");
}

if (File.Exists(@"\serverFilesBook1.xls"))
       {
            ButCrear.Visible = false;
            BtnChk.Visible = true;`

        }

function test() {
    var Excel = new ActiveXObject("Excel.Application");
    Excel.Visible = true;
    Excel.Workbooks.Open("teste.xlsx");
  }

function test() {
    var Excel = new ActiveXObject("Excel.Application");
    Excel.Visible = true;
    Excel.Workbooks.Open("/upload/teste.xlsx");
  }