Can someone help me simplify this?

This function seems really bulky and I'm pretty sure that it can be simplified down. Can someone help me do this?

Code:

int sd_solve(int x, int y, int n){              //Checks if n is a valid number to input

    int i,j,k;
                                                //Checking the boxes
                                                //For this, we will divide the sudoku into
                                                //nine sections (top-left, top-mid, top-right,
                                                //mid-left, mid-mid, mid-right, bottom-left
                                                //bottom-mid, bottom-right) and check if n is
                                                //already in the section that we are trying to
                                                //solve.

    if (y<3) {                                //If n will be in the top section
        if (x<3) {                                //If n will be in the top-left
            for(i=0;i<3;i++){
                for(j=0;j<3;j++){
                    if(n==sd_finish[i][j]) {
                        return 0;
                    }
                }
            }
        }
        else if(x<6) {                           //If n will be in the top-mid
            for(i=3;i<6;i++){
                 for(j=0;j<3;j++){
                    if(n==sd_finish[i][j]) {
                        return 0;
                    }
                }
            }
        }
        else {                                      //If n will be in the top-right
            for(i=6;i<9;i++){
                 for(j=0;j<3;j++){
                    if(n==sd_finish[i][j]) {
                        return 0;
                    }
                }
            }
        }
    }
    else if(y<6) {                           //If n will be in the mid section
        if(x<3) {                                //If n will be in the mid-left
            for(i=0;i<3;i++){
                 for(j=3;j<6;j++){
                    if(n==sd_finish[i][j]) {
                        return 0;
                    }
                }
            }
        }
        else if(x<6) {                           //If n will be in the mid-mid
            for(i=3;i<6;i++) {
                for(j=3;j<6;j++) {
                    if(n==sd_finish[i][j]) {
                        return 0;
                    }
                }
            }
        }
        else {                                      //If n will be in the mid-right
            for(i=6;i<9;i++) {
                for(j=3;j<6;j++) {
                    if(n==sd_finish[i][j]) {
                        return 0;
                    }
                }
            }
        }
    }
    else {                                      //If n will be in the bottom section
        if(x<3) {                                //If n will be in the bottom-left
            for(i=0;i<3;i++) {
                for(j=6;j<9;j++) {
                    if(n==sd_finish[i][j]) {
                        return 0;
                    }
                }
            }
        }
        else if(x<6) {                           //If n will be in the bottom-mid
            for(i=3;i<6;i++) {
                for(j=6;j<9;j++) {
                    if(n==sd_finish[i][j]) {
                        return 0;
                    }
                }
            }
        }
        else {                                      //If n will be in the bottom-right
            for(i=6;i<9;i++) {
                for(j=6;j<9;j++) {
                    if(n==sd_finish[i][j]) {
                        return 0;
                    }
                }
            }
        }
    }

    for (j = 0; j < 9; j++) {                   //Checks the row and column n is in
        if (n == sd_finish[j][y] || n == sd_finish[x][j]) {
            return 0;
        }
    }

    return n;                                   //If everything is fine, it returns n
}

It's part of a Sudoku code and another function is basically calling this function with a possible value n when it sees a blank and checks the box the number will be in and the horizontal and vertical possibilities.

I'm almost positive this can be simplified it's just that I can't figure it out :/

Didn't I just show you how to simplify that yesterday?


Quzah.