If you are using the LO Agent you can configure situation formula based on regular expression to fit your needs.
Below the LO Agent User Guide
http://pic.dhe.ibm.com/infocenter/tivihelp/v15r1/topic/com.ibm.itm.doc_6.2.3fp1/logfileagent623fp2_user.pdf
Take a look at the "Log File RegEx Statistics attribute group" section:
The Log File RegEx Statistics attribute group contains information that shows the statistics of the log file
regular expression search expressions. Regular expressions can be used to filter records or to define
records. This attribute group shows information about both types. When the Result Type attribute value
is INCLUDE or EXCLUDE, the filter is used to filter records;
Hope this helps
I don't have the reputation yet to post a comment but I'd have liked to ask if you are using the Tivoli Log File Agent (lo) of the Unix Log Agent (ul) before answering.