Thank you John and Bernie for your reply to my posting. I've been away for a few days, hence the delay in my response.
Bernie: I hadn't thought about the relevant programme being case sensitive which it obviously is from what John has to say.
I am 'office trained' and one of the first lessons I had was, when filing, use the Aa, Ab, Ac, system with the latest date on top (which we called the B.T. system), because most people know how to read telephone directories which makes it is easier for anyone to find the documents in the filing cabinet. Having used this system success-fully all my working life, I'm ashamed to say I didn't even think of it as a possible answer to the question. Must have been a 'senior moment' ....
Thanks again lads.