Can anyone help me here....?

I've written a standalone application using VB/VBA to make changes to
an existing Excel file. The app works but the Excel file must be
closed. After the app is run the file can be opened to see the
results. The Question: Is there a way to run my app against the Excel
file while its **open** then perform some kind of refresh to see the
changes?? I'd like to avoid the open/close cycle if at all
possible....

Any/all help would be much appreciated...
Thanks in advance.

Don-