The others have emphasized that the backend DB controls this. I'll emphasize the OTHER facet of this problem, which Pat Hartman mentioned. If you are exposing your tables to your users, you have already lost this battle. If you only expose things via a form then you can use the form's abilities to block users from seeing/doing too much.
Search this forum for "Securing a database." That will provide MANY discussions of how to selectively protect your tables.