how to configure syslog.conf so su would NOT log into /var/log/messages

[ssloh]

Hi folks,

Wheneven I do a "su abc" it was logged under /var/log/messages.
How can I configure /etc/syslog.conf so that when I do a "su abc" below messages would not appear in /var/log/messages.
I still want other user to log to /var/log/messages when they issue "su user"

Oct 24 14:53:41 linux01 su(pam_unix)[586]: session opened for user abc by (uid=0)
Oct 24 14:53:42 linux01 su(pam_unix)[586]: session closed for user abc

Thanks