Microsoft.Office.Interop.Excel.Application excel = null;
Microsoft.Office.Interop.Excel.Workbook wb = null;

object  missing  = Type.Missing;

try  {

excel = new Microsoft.Office.Interop.Excel.Application();
wb = excel.Workbooks.Open("c:\\test.xls", missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing);
excel.Visible = true;
wb.Activate();

}  catch (COMException ex) {
MessageBox.Show("Error accessing Excel: " + ex.ToString());

} catch (Exception ex) {
MessageBox.Show("Error: " + ex.ToString());

}