What I understand from the project description you have posted is that you already have a algorithm in mind and only want it to be implemented.
If I may, I would like to suggest a solution which will get the sudoku solved very elegantly. What I was thinking of was to use a 5-Dimensional integer array for storage, manupilation and also the for the storage of the final solution. If your goal is to get and solution and not "simply" the implementation of the algorithm you already have then I can provide with you with the details.
Another question that I have for you is, what kind of UI would you prefer for this "sudoku <b><i>Removed by Freelancer.com Admin for breaching our Terms and Conditions</i></b>". I wanted to ask it, because UI is the most time consuming part of the application development.