Grabbing cookies off page, using webkit?

Don't know if its possible but a bot I am writing needs to log on to a website the problem is, only the bare details are initially written to cookie, the secondary ones required to do anything are calculated by javascript.

Do i have to sort through dozens of .js files or can I post the details via a browser than grab the cookies need?

Its a sad day when you start an 'interesting solution required' thread and every reply is saging it :(