In the certificates that are issued from my Enterprise CA, I'd like to have multiple (two) OCSP URLs - one for an internal HTTP location and a second one for an "external" HTTP location. Is this possible in the same way that it is for CDPs and AIAs? Thanks.

yes. You can add multiple OCSP urls. Processing behavior is the same as for other CDP/AIA urls. If first URL fails, client will try second URL and this repeats until certificate stauts is determined or this is the last URL in the list. However you should limit URL count in CDP/AIA extansions to avoid large delays in certificate checking. http://www.sysadmins.lv