Interntal and external access

Dear all,

I need to enable internal and external access to my RT. Internal (LAN)
access works with NTLM authentication, external (Internet) should work
with Apache authentication.
I tried using two virtual hosts, internal on port 80, external on port
443 (https). It failed because of $WebBaseURL, where I have to define
ether http or https.
Is there a way to enable this without setting up two RT instances?