How do I create an exchange certificate with openssl?

We've been using makecert to generate certificates for testing, and in some environments, we have access to Active Directory Certificate Services, for which we have certificate templates we can use to create the various certificates our app needs, but we'd like to set up a batch file we can run to create all the certs required for a new installation in one go.

At the moment, I'm using openssl - and so far, things are going really well. I've hit a bit of a snag, though - one of our certificates is used for key exchange (in makecert, this would be -sky Exchange) ... and I can't seem to find an option for that in openssl. It has to be there, but I've been searching and searching through their documentation and I'm not finding it - I assume it's called something else..or something.

Help?