Since past Challenge was easy to solve lets vote for something different
Pentomino Solver
Lots of solvers in java , c .... but none in vba excel
Information on Pentomino click below
http://en.wikipedia.org/wiki/Pentomino
Sudoku solver
I think it is more easy to make a solver than to solve a difficult Sudoku puzzle
Information on Sudoku click below
http://en.wikipedia.org/wiki/SuDoku
The faster Solver is the Best Solver
Pentomino Solver
Lots of solvers in java , c .... but none in vba excel
Information on Pentomino click below
http://en.wikipedia.org/wiki/Pentomino
Sudoku solver
I think it is more easy to make a solver than to solve a difficult Sudoku puzzle
Information on Sudoku click below
http://en.wikipedia.org/wiki/SuDoku
The faster Solver is the Best Solver