I have a slight problem that I need to know if it possible to overcome:

I have written a VB program using Access as data storage. I have a column in a table that requires unique entries. (Meaning that no 2 fields can have the same data.) I have a primary key set on that field. Is it possible to check what the user enters against the entries in the database before the new entry gets added to the database? If so, how is it done?