Not possible? How to accomplish " city / area " type relation with taxonomy or category module?

Hello,

I am working on a local review site (like yelp).

For simplicity purposes, lets say I need only 3 fields while adding a review:

1. City - preconfigured drop down list of all cities
2. Area - *free tagging box* where people can add in the name of the area in a city
3. Review Body - detailed review body

So far so good.

However, I would like to create a view of all reviews such that when the user chooses a city, *only the areas of that city* come up dynamically in the area box.

i.e. if user chooses:

City -> "New York"

then only:

Area -> "Manhattan"
"Queens"

should come up in the "Area" box.
And not "Chinatown" which should come up only for "San Francisco".

i.e. there should be an onchange trigger from the City dropdown populating the Area dropdown, based on the selection.

I cant seem to achieve this functionality, atleast with the taxonomy module.
i.e. all areas show up for every city, which confuses the user.

Is this at all possible with taxonomy or category modules?

Thanks in advance for your help,
Reggie