System logs setup to log spesific messages

Hi. I have been using regular .conf files for rsyslog to log my iptables that are beeing dropped, ex: INPUT-DROP:

And I wanted to try out the option to set this up in webmin. I added the log file, and selected KERNEL, but I can not find anywhere to spesify the MSG STARTWITH to only log the needed messages to the spesific file.

Typical log entry:

Is it possible to do this? and how? Or should this really be added to webmin? I think yes =)

Thanks! -Tom