private void display_combination()
    {
        for (int i = 0; i < MAX_INPUT; i++)
        {
            switch(combination[i])
            {
                case 0: button_flash(this.Up_Button); break;
                case 1: button_flash(this.Down_Button); break;
                case 2: button_flash(this.Left_Button); break;
                case 3: button_flash(this.Right_Button); break;
            }
        }
    }

void button_flash(Button b)
    {
        b.IsEnabled.Equals(0);
        //perhaps a pause her and then enable the button again?

    }