categories

Apologies for posting this twice but I have lost my original request and forgot to tick the box to be notified of replies.

I need a way to either:
a. Have dynamically updating drop down boxes based upon categories/sub categories. This is for admin area not front end. I will have lots of categories and sub categories and I do not want my client to have to scroll through pages of them to locate the correct one when creating a new post. Example: Client selects United Kingdom from drop down menu which then loads a 2nd drop menu and they select a UK city.
OR
b. If the above is not feasible then is it at least possible to have the categories showing as drop down boxes rather than pages and pages of each category/sub category?

There is a great module for Drupal that allows me to do this but I would much rather use WordPress.

Apologies if you have read a previous post of mine but as I say I cant seem to find it.

Any help would be grateful.

Cheers
Paul