What you describe are called Conditional Value Lists.
Take a look at this article to see how to do it:
As for the coordinate fields, you could use a Lookup based the regional coordinates.
Thankyou it was exactly what I needed!!!
Here is a link to a demo file you might find useful: http://www.4shared.com/file/f8NsU2DJ/ConditionalValueListDemo.html
Here is a link to a forum thread that discusses how to set up lookups: Auto Fill
thanks I did it!