data entry behaviour

Hi

One of my people is entering data into an Access 2003 table.

What happens is that if they enter 126 in a field, then use the down arrow key to move to the field beneath and type 127, they find that using the down arrow key again will automatically place 128 in the field below.

Is there a way to stop this behaviour? It would be great if using the down arrow key simply moved the focus to the field below without automatically inputting data.

Thanks