diff --git a/sudoku.lispbm b/sudoku.lispbm
index a1d2184..c66583a 100644
--- a/sudoku.lispbm
+++ b/sudoku.lispbm
@@ -19,9 +19,40 @@
     (((? x))
         (map (lambda (y) (list y)) x))
     (((? x) . (? xs))
+     (if (list? x)
         (zipWith
             cons
             x
-            (transpose xs)))))
+            (transpose xs))
+        ('error)))
+    (_ 'error)))
 
 (defun getCol (grid x) (getRow (transpose grid) x))
+
+(defun MatrixToList (m) (foldr append nil m))
+
+(defun getSubMatrix (m startcol stopcol startrow stoprow)
+  (let ((f (lambda (x start stop) (take (drop x start) (- (+ 1 stop) start)))))
+   (map (lambda (x) (f x startcol stopcol)) (f m startrow stoprow))))
+
+
+(defun getSubGridAsList (m x)
+  (if (and (>= x 0) (< x 9))
+      (let ((sr (* (// x 3) 3))
+            (er (+ sr 2))
+            (sc (* (mod x 3) 3))
+            (ec (+ sc 2)))
+        (matrixToList (getSubMatrix m sr er sc ec)))
+      'error))
+
+(define exampleGrid
+  '(
+    (1 2 3 4 5 6 7 8 9)
+    (2 3 4 5 6 7 8 9 1)
+    (3 4 5 6 7 8 9 1 2)
+    (4 5 6 7 8 9 1 2 3)
+    (5 6 7 8 9 1 2 3 4)
+    (6 7 8 9 1 2 3 4 5)
+    (7 8 9 1 2 3 4 5 6)
+    (8 9 1 2 3 4 5 6 7)
+    (9 1 2 3 4 5 6 7 8)))