Redirector that reads HTTP header?

Hi,

I'm looking for a redirector that's able to read some properties out of
the http header. Are there any?
What I what to do is check if the header contains a LDAP dn and if it
does then redirect it.
This is for a reverse proxy (so my users are outside my LAN, on our
extranet). I don't want to authenticate them, because we do this by
using PKI. I just want to redirect them to our secure (PKI) site on the
basis of their HTTP header properties.

Has anyone done something like this?

Best regards,

Danny Kruitbosch