Hi Chuck,
Sorry I didn't get back to you sooner. I came back later that night and had a brainwave.
I just discovered how to use extend. Which I knew existed but got the wrong end of the stick on it. I suddenly realized what the problem was...I had referenced non-repeating fields!
Ta very much for your follow-up though and I am sure that I will find something else to mess up. This will teach me to not look at a product for 10 years and then expect to go back just like that.