Add keyboard up/down/enter support to search field

Hi, For a webshop I have a searchbox that looks like the one in the "additional files" below. It works well, but it lacks one important feature: Keyboard support. With "keyboard support" I am thinking in direction on Facebook's friend search. It suggest friends that fit your search keywords, and you kan use the keyboard up/down arrows to choose wich friend you are looking for. By pressing enter you go to that friends page - or in our case: a specified url. Google Instant search is another example. You start typing a word, and as you are typing a word that get a hit - you can simply use up/down keys to select it and press enter. Let me know if something is unclear. All I want you to do is implement it to my existing searchbox, or rewrite my script to something that can do this. I have a live example and sample code ready if you want to take a closer look. It will also need to be lightweight. Thank you!