Check if XLS file is open and close it

Determine if Excel file is open. If it is open in MS Excel, it can be closed.

Determine if Excel file is open. If it is open in MS Excel, it can be closed.

USAGE
isopen = xls_check_if_open(xlsfile)
isopen = xls_check_if_open(xlsfile,action)

INPUT
- XLSFILE: name of the Excel file
- ACTION: 'close' (closes file if it is open) or '' (do nothing). Option 'close' only works with MS Excel.

OUTPUT
- ISOPEN:
1 if XLSFILE is open
0 if XLSFILE is not open
10 if XLSFILE was closed
11 if XLSFILE is open and could not be closed
-1 if an error occurred