HTTPS Post Response - Kaiser CAMS

I'm looking for some help with an HTTPS POST Response issue.

Our company offers Kaiser Permanente (California) as one of our health benefits options for a subset of our workforce.  Kaiser is implementing a new (required) step for employees that elect this plan during the enrollment process.  Basically, if an employee elects the Kaiser plan in ESS, we are required to redirect them to the Kaiser website so they can read and accept/reject their arbitration agreement.

The only option they provide is by doing an HTTPS POST with the required data to their site.  When the employee responds on their page, then Kaiser returns a response to a URL we designate.  We then have to parse the response to determine whether the employee accepted or declined the arbitration agreement.

By modifying our ESS enrollment process, I have been able to get the POST to work correctly and it is correctly going to the "return" URL on our site after an election is made, but I can't figure out how to get to their response to parse.

Our best guess is that this will require some sort of server-side scripting to make this happen, but I'm at a loss.  Have any of you done anything like this?  Can you point me in the right direction?

NOTE:  Although I have quite a bit of Lawson/Infor development experience, I have very little background in ESS or Web development, so any help would be appreciated.

Thanks!

Kelly