4 KudoZ points awarded for this answer. Comment: "thanks loads cindy....i was in a fret at the time, working away from home and connecting via ciber....(surrounded by millions of teenagers playing some noisy arcade game......i felt so OLD in there), and was in a bit of a whiz for time and just couldn't remember a thing about my school-time physics (not that I paid much attention at the time anyway)....saved the day again...thanks.....will be emailing you with an invoicing question soon if that's ok by you???...cuidate.."