A Lookup Field in a Table is considered to be a very bad idea by many experienced Access developers, especially when done by inexperienced developers! For the reasons why read the article "The Evils of Lookup Fields in Tables" here:
http://mvps.org/access/lookupfields.htm
Note that this refers to Lookup Fields/Comboboxes in Tables not to Comboboxes in Forms, being used to lookup Records. That is something else all together.
Linq ;0)>
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007