Plugin to change page content based on cookie or user variable

I have a client who runs a business with offices that cover different areas. Their coverage regions are broken down by zip code and they want to be able to have the content on a couple of pages change based on the user’s stated zip code. I.e. they have a contact page with address and telephone numbers that they want to show the correct office contact info if they have already provided their zip code, and generic corporate info if they have not. I can probably code this easily enough, but I’m curious if anyone know of any plugins that might do this already, or that might be a good starting point for such a plugin.

Thanks in advance.