In a message dated 19/12/2004 17:40:04 GMT Standard Time, bones@xxxxxxx writes: explaining Reverse Polish Notation that is used for the gauge operation. = Way beyond me Bones, Thanks for that, I'll make a start looking at some XML files. I have used Reverse Polish Notation, I found it first on HP Calculators back in the seventies. I once heard it described using an analogy of the old sprung plate racks in the canteen, you push things down onto the stack and they pop up in the reverse order you pushed them down. The reason for it is that you can easily write a program to resolve RPN formulae, much easier that to solve a regular formula, you just continually parse from the top of the stack downwards until it is exhausted. Mind you, that was a long time ago.......... Frank T.