The mat2cell function will likely do what you want.
Note that assigning each matrix to a different variable is not advisable. Keep them as the cell array, and refer to them as elements of it, using subscripts.
Dividing a (9x9) matrix into 9 (3x3) matrices would work as:
Adiv = mat2cell(A, [1 1 1]*3, [1 1 1]*3);