Well, you could insert a hyperlink to the file in question by pressing
<Ctrl>+K or click INSERT in the menu and select HYPERLINK. The link can be
to an existing file or web page, a location in the current document, a new
document or an email address.
Kevin:
Thanks for the response. I found eventually what I was looking for. In
Tools, Options, Edit - I needed to disable the function permitting Editing
Directly In Cell.