You can put anything you'd like into the arslog script. Scripts are usually written in a UNIX script language, so that it's fast to start up. You can do anything with any of the variables you're passed, so if you have "ICN_USER" as a User ID, you can simply do an:
LOG_FILE=LogFileName-`date +%Y%m%d`
if [[ $4 == "ICN_USER" ]] ; then
print "$8" >> $LOG_FILE
fi
But just an FYI - it's REALLY important that your code is *FAST*. If you're going to call it hundreds of thousands of times a day, even if it takes half a second to run, it can severely disrupt your CMOD server.
Is there a reason you're not simply doing queries on your System Log the next day? What exactly are you trying to accomplish with this?
-JD.