[Exim] pipe command

Hi,

is it possible to do a lsearch-lookup in a command of a pipe
transport?

The following command seems not to work...

command = /opt/mail2news/mail2news ${lookup
{$header_list-post}lsearch{/etc/exim/mailinglists}}

Where the /etc/exim/mailinglists has the following content:

exim-users@???:            lists.exim-users

Any help is greatly appreciated.

Thanx, Michael