[exim] Ldap lookup selectively add a port for certain users

I need to setup a pilot for a new mail server I have the ldap lookup
working for the current server the new mail server will be running on a
different port I want to change the mailHost attribute in the
directory server to the new server so that it extracts the mailHost for
the user from the directory. How can i get exim to extract the mailhost
and then if the host is host.domain.com then it must just send the mail
to the normal port 25. If the host is host2.domain.com then it must add
a port to the end so that the smtp request get's rerouted to
host2.domain.com:port. I can't add the port to the LDAP mailHost it
won't allow me to do that.

Carinus