Exclude SQL Log messages from Idera Alerts for 'SQL Server Error Log' Alert

Need to able to exclude certain SQL Error log messages from triggering Idera Alerts.  These feature is useful to reduce unnecessary alert emails .  Thank you.

Tried using the negate, eg '!user1' , in the current  regular expression to exclude error logs from alerting (advance option). But it does not work.

Please implement 'exclude' option in the next release.  Thank you