Check for open Excel workbook and then close it and Excel

I use a program that imports into Excel that requires that the workbook is
closed prior to the import.

How do you check to see if an Excel workbook is open, and then close the
workbook?

How do you then look to see if Excel is still running and then close it
(Excel.exe)?

I already know how to open an instance of Excel, use it, and then close it,
but I have not figured out how to check for an already open instance of a
workbook and/or Excel.

Thanks,
--

Randy
.