#if weis
> Can anyone tell me what to do here. Excel is getting quick and good
> results, so there must be a way.

I seem to remember using something called the Newton-Raphson (sp ?) method
for finding a point on a graph by guessing and then refining.

I've completely forgotten how I did it, but I wrote a program to do this
some years ago. Perhaps this is the solution ?

Cheers,
Rik