205897 Simple Postal Code Verifcation

We are a Landscaping company currently running a 10 page informative website. We want to place a small box on our nav bar that allows users to verify (via their postal code) whether or not we service their area. our website is [login to view URL] visit the customer section and you will see a brown box to the left on the nav bar. This is where the verification box needs to be placed we want something similar to how MS verifies username availability when setting up an MS Live account: [login to view URL];ts=4305123&sh=FAZn&ru=http%3a%2f%[login to view URL]%2f%3fnewuser%3dyes&rx=http%3a%2f%[login to view URL]%2fmail%2foptions&rollrs=03&lic=1