IP masker or changer to test Pay Per Click ads?

I work for an online advertising company. We sell people PPC ad space and help put the ads and campaigns together for them.
It is a relatively new form of advertising for us, up until now we’ve been doing only search directory listings.
Recently, I had a customer who was located in the state of Connecticut but he wanted to target his ads only in California for a trade show they were attending out there. He asked how he could test his ads in Connecticut since they were only being targeted in California, and unfortunately I didn’t have an answer for him.
Is there some sort of online web site or tool that my company and our customers can use to do this sort of testing? Something that will allow to do online web searching but as if we were connected in a different state?
Thanks in advance!

See original post by ADK