[exim] limit errors_to= router specific

Hi all,
how to limit errors_to= to a single router?
I have a construction with several routers. For one router the 'mail
delivery failed' should be sent to me otherwise of course to the sender
back. In my configuration I get ALL 'Mail delivery faild' messages.

Here the part of my exim4.conf

lists:
         driver = redirect
# allow_fail
         errors_to = ${lookup pgsql {select 'sigl@???'}{$value}}
         data = ${lookup pgsql{select 
process_list('$local_part','$domain')}}

# this router is only for dummy reasons, set on 4.7.06 sigl
# that the errors_to statement is not operative for usual bounce
#addresses
#This Router is the last router

unknown_user:
         driver = redirect
         data = :unknown:
         cannot_route_message = \
                 <${local_part}@${domain}> is not a known user on this sy

Regards
Rainer Sigl

-- 
-----------------
Rainer Sigl,                      | email: sigl@???
MPI f. extraterrestrische Physik, | phone: +49 (89) 30000-3557
Postfach 1312,                    | fax:   +49 (89) 30000-3569
D-85741 Garching, Germany         | web:   http://www.mpe.mpg.de/~sigl/