Currently, pressing "tab" on a form has one behavior: move one box to the right. This can make for some pretty unintuitive user interfaces - see the image for an example. If you have two address columns, there's no way to tab down the columns; the focus will bounce back and forth between them.

Please include a way to modify this, with a way to change tab direction to vertical, or to a custom tab order specified by the app developer. Access has a nice tab order function you could look at for inspiration.