Captive Portal

I have a Windows Server 2003 that I have setup Certificate Services on and it is my Enterprise CA.  I can generate .cer files from the website that it installs into IIS and I have even put the certificates I have generated into IIS for an SSL site there.  How can I generate a SSL certificate AND get a private key to enable SSL on the Captive Portal site?  I am interested in figuring out how to do it on Win Server 2003 but I am willing to do it via another method if someone has one that works.  Thanks