Quick-Jump keyword box

Hi, I am nearing the completion of my site and am missing one last feature script-wise. The thing I'm talking about is a 'Quick-Jump' box on the splash page, where the visitor can enter a pre-defined keyword to be taken to a page.

An example of this is the keyword/search box on TVNZ.CO.NZ- if you type in 'nz idol', you go to the NZ Idol homepage. If you type in a keyword that is not predefined, you get taken to the search page.

I don't want a search function, just a simple javascript input text box and a go button. A list of predefined keywords, so if the visitor types in 'login' for example, they get taken to the 'login/login.php' page. If they type in a keyword that is not listed, they get taken to a error.htm page or someting.

If anyone could help me out or point me in the right direction, I'd be really grateful.

Thanks for your time!