A client has asked me to tailor the content of their homepage based on how the user got there from Google. His example is something like:

If a user searches Google for Cars in Barcelona, then the homepage has content based on cars in Barcelona.

I can't see how this would be possible - would I need to have 20 or so different content blocks for the homepage to cover all of the areas they would like to promote? How would I then get Google to display the correct content based on the search and how would I get Google to index them all?

Bit confused by this one, so any help would be greatly appreciated!

Thanks