Up and Down Arrow Keys in a MS Access 2003 Subform

I am using an Access form with a subform for data entry. The subform is like a grid and the end users would like to be able to move up and down between rows in the grid staying in a specific field using the arrow keys. The arrow keys let you move from field to field within the record but not up and down between records/rows. The subform is linked to a different table than the main form.

Is there a relatively simple way to do this?