I wonder if the following is possible with JoomSEF

I would like to generate a dynamic landing article for various locations through the use of inserting the URL Parameters throughout the content via php (i have the extension that does this already) and custom URL's however, want to control the urls to prevent anything being custom-entered.

IE:
default article = www.mysite.com/category/article
dynamic article url = www.mysite.com/category/article/arizona (or /texas/ or /maine/, etc)
however,
this would default as a '404' = www.mysite.com/category/article/sunshine (because i have not entered it 'somewhere')

An example would be www.hungryhouse.co.uk which, when you enter your location, the URL changes to include town/postcode... this is picked up by google, too. - in reverse, if you google search "hungry house me14" you see how the spidered URL's generate the dynamic page content and meta tags, etc at the site - this is essentially what I am trying to achieve.