I goofed... I was using notepad over and over to try and replicate the file being accessed. I found that notepad doesn't cause the file to show as open. When I tried Excel, right before doing my post, I goofed and opened my output file instead of my input file.
I still need to do some testing when the financial system is writing a file to make sure it works the same way or if I need to take your suggestion and look at the file handle.