First off, are you speaking Lookup fields as defined in a Table? Or is your lookup field done through a Combobox on a Form?
Lookup fields defined in Tables are frowned upon by experienced developers, for a number of reasons, explained here:
The Evils of Lookup Fields in Tables
Comboboxes in Forms, which are sometimes called "lookup fields" are both safe and handy. If this is what you're attempting, let us see the code you're currently attempting to use.
Linq ;0)>
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007