Even though the workbook is closed, NumberOfSheets returns 1 and I get no error.
...
'add some cells etc
wb.Write
wb.Close
Log("sheetcount=" & wb.NumberOfSheets)
But if I try another wb.close it raises an error, as expected.
Unlike alienhunter's experience, I find that if the jar is still running, I still cannot open the xls from another Windows folder. I wonder if wb.close is not properly closing the file and releasing the lock. Can someone confirm the above?