@grumpy2,
You won't believe the hours/days I have spent on this one question! Not lazy just frustrated! I have approached it from every angle (apart from the right one obviously :-)).
I am usually a pretty thorough researcher but must be barking up the wrong trees so far. I am not after being given the answer by the way!
It's amazing how easy some questions are!, once you know the answer. Just like most quizzes etc.
Thanks anyway, I will keep on looking. No sleep tonight I fear :-)