C# :: Sudoku Solver Using Loops / Textboxes

As it is known there are nine boxes and in each box we can put numbers 1-9 without repetition. I am trying to check a given filled Sudoku puzzle whether appropriate numbers are inserted in each of the nine boxes. For the time being I don't consider row repetition and column repetition. I wrote the code using loops and condition

I used 9*9 text-boxes. The names of the textboxes is sequential like for example for the first box
txt11,txt12,txt13
txt14,txt15,txt16
txt17,txt18,txt19

Actually, I used also the controls id to access the text boxes, and each box is checking with the neighboring boxes for equality both in forward -> and backward <-

image

So here is the code

public void BoxCheck() {
int start = 82, end = 74;
int i, b, f;
for (int p = 1; p <= 9; p++, start -= 9, end -= 9) {
richTextBox1.AppendText("
Box " + 1);

[Code] ....

This works pretty fine, but is is the right way to do it? it is efficient? Remember for a full checking I have to include row check and column check as well, this is just for checking within each of the 9 boxes in Sudoku.