[exim] Ldap in Router works well but i want it to reject if …

I am setting up a routing box for internal mail. I have a exim that picks
up the mail and then defers it where a scanner picks up the mail and puts
it back into a "active queue" this is then moniterd by a queue runner
process that will pick up the mail and deliver it. I have the router
below for delivery which I compiled from the archive. Can someone help me
to modify it so that it will deliver if the address data is valid and
reject with a message if it isn't.

ldap_user:
  driver = manualroute
  domains = mrc.ac.za
    address_data = ${lookup ldap 
{ldap://arnor.mrc.ac.za/o=intramural,o=msp?uid,mailhost?sub?\

(|(mail=$local_part@$domain)(mailAlternateAddress=$local_part@$domain))}{$value}fail}
condition = ${if match {$local_part}{extract{uid}{$address_data}}}
transport = remote_smtp
route_list = mrc.ac.za ${extract{mailhost}{$address_data}}

Carinus