Erk! It seems that this problem has been exercising mathematicians and so for no linear solution has been found. All present methods use iterative algorithms (using a guess to find a better guess until no further improvement can be made). There are algorithms of varying complexity and which take more or less time to find the solution but I don't think any of these can be implemented in a straight spreadsheet - needs programming.

Take a look here

http://www.delphiforfun.org/programs...ing_points.htm