Tom,

Thanks for the prompt reply, but I think you misunderstood my question.

My cleanup function correctly clears all my excel references and calls the
Quit() function...so whenever the cleanup function gets called, everything is
fine. My problem is that when a user manually clicks the close button on an
excel window, I am not being able to detect that close event, and thus my
cleanup function does not even get called.

Does that make sense? Below is my cleanup function which works correctly.

private void cleanUpExcel()
{
   if (excelApplication != null)
   {
        try
        {
             excelApplication.DisplayAlerts = false;
             foreach (Excel.Workbook workbook in excelApplication.Workbooks)
             {
                 foreach (Excel.Worksheet worksheet in workbook.Worksheets)
                 {
                     
System.Runtime.InteropServices.Marshal.ReleaseComObject(worksheet);
                 }
                 workbook.Close(false, Type.Missing, Type.Missing);
                 
System.Runtime.InteropServices.Marshal.ReleaseComObject(workbook);
             }
             
System.Runtime.InteropServices.Marshal.ReleaseComObject(excelApplication.Workbooks);
             excelApplication.Quit();
             
System.Runtime.InteropServices.Marshal.ReleaseComObject(excelApplication);
         }
         catch (Exception)
         {
             //Excel may have been closed via Windows Task Manager.  Skip
the close.
          }
     }
}

Mehul.