game of nim wpf

[Chargerfan]

i am writing the game of nim in wpf and so far i have figured out how display the objects and added a mouse down event to highlight which object the user has selected to remove. Now my question is how do i make it so that the user can only select objects from the same row? Here is the code from the mouse down event:

private void canvas1_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            p = e.GetPosition(canvas1);
            brushColor = Brushes.Blue;
            foreach (object obj in canvas1.Children)
            {
                for (int i = 0; i < rows; i++)
                {
                    for (int j = 0; j < columns; j++)
                    {
                        if (((Rectangle)obj).IsMouseDirectlyOver)
                        {
                            if (p.Y >= ((Rectangle)obj).Height && p.Y <= ((Rectangle)obj).Height*j + 45.5)
                            {
                                ((Rectangle)obj).Fill = brushColor;
                                Console.WriteLine("p = " + p);
                                return;
                            }
                        }
                    }
                }
            }
        }