i imagine the script would have to point to your cookies folder somehow, thus auto sign in like with microB would be possible. but i'm just guessing. dont ask me how to make it point anywhere, cos unless the answer is draw a big ascii arrow i dont know jack. :/

EDIT: unless facebook sign in supports the web address tyoe sign in.... e.g. username:password@webaddress.com in the url field, then you would just need to edit the url in the script to have your username and password. again, just guessing, test for yourself!