Sylvain
I'd be inclined to use a 2-column lookup with the second column being set in code rather than directly entered- so the user chooses Seattle | Washington or Washington | Washington rather than entering separately.
That's an off-the-cuff answer, others may have better suggestions from experience.
Regards
JR
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1