I write formulas using the function variables fn1 - fn4. It's then very easy to simply hit Z and keep plugging in different functions and seeing what happens. I can try hundreds of combinations in a relatively short time. Bill Rossi <A HREF="http://members.aol.com/billatny">http://members.aol.com/billatny</A> <A HREF="http://www.arts4u.org/rossi">http://www.arts4u.org/rossi</A>