I don't think you will get much help here for this type of question. If you look at the responses to this recent node, you will see why.
This can be done with LWP and the information needed is in the LWP modules docs. However, I wouldn't use your site for numerous security reasons. If your script is for personal use, I am sure that there are a few people who could help.
Comment on Re: Using LWP to log-in to an external website
it's for me to check news headlines at excite.com with my palm pilot.
I realize it must be scary to think that someone could steal your excite.com username/password and know what stocks you own but I think most people would be willing to chance it.