[syslog-ng] Inserting text in syslog messages

Dear All, Does anybody knows how to insert some string in a message that will be apended in log files ? I mean, imagine that syslog-ng receives this message to insert in /var/log/auth.log. Jan 31 13:18:01 host sshd[6278]: Accepted keyboard-interactive/pam for user from 10.10.0.29 port 49105 ssh2 And I would like to insert some text together, resulting in some like this Jan 31 13:18:01 host sshd[6278]: Accepted keyboard-interactive/pam for root from 10.10.0.29 port 49105 ssh2 - service xyz for user root How can I include this string " - service xyz for user root" ? I know that it's possible, but I didn't find how to. Thanks in advance Gustavo