Editable Dynamic Table

A few things to note:

• Area is updated whenever length or width changes
• MVC is used. In other words there is Box object. Changes in length or width text boxes trigger an update of the box's state. An update of the box's state triggers and update of the area text box. A bit over kill for this little example, but MVC is very usefull for more complex examples.
• The up and down arrows can be used to move from cell to cell (Excel style) - this feature is implemented a bit half-ass but it still is a great teaching example.