Can anyone help me with this?

I'm looking for a javascript that will add a cookie when the page loads, then read the cookies value whenever the user returns to that page, adding the coockie value to a hidden text field. I can do this with ASP, but the client's page is an HTML page that cannot be changed to an ASP page. Any help is greatly appreciated! Thank you.

Out of curiosity, why would the cookie need to be added to a hidden form field? It's already in a cookie, so accessible via Javascript and to the server...

I'm also accustomed to working with cookies only from the server, and was scratching my head recently when asked to put together an offline pseudo-website, to go onto a CD, for a lesson plan being sold to students. I needed answers to be saveable on textareas, so they needed to be saved onto a cookie and it needed to happen with JavaScript alone.

Here is the guide I used: http://www.quirksmode.org/js/cookies.html
Note you only really need to know how to use the three functions PPK outlines.

@Jeremy: maybe it's for a form that is being submitted to an external site?