Check if file is open and open if closed

Hi,
I have code which will check if the file "C of S.xls" is open. Ideally, if it is open, the sub will exit but if it it closed, the sub will open "C of S.xls".
When the file is already open, everything works fine. However, when the file is closed, I get the "subscript out of range, Run time error 9" debug error at the point in the routine where it looks for the "C of S.xls" file.
How can I avoid this happening?
I have attached the file.
Thanks.

Jockster