Thanks for your help. This is someone else's addon that I was updating (I had got his permission and was going to joint release it as both a lite version and a full version) but my personal coding skills are poor (about the best I can do is alter someone else's code. I am not a programmer by any stretch of my imagination) but it looks like I will have to try and rebuild this whole thing from scratch or abandon it. Well if I persevere I will be able to call myself an addon author.
