I am just learning Trisul and keep finding difficulty with setting up my custom alerting. Particularly TCA alerts and the syntax regarding the target key. I'm assuming it is possible to specify more than one target key in the parameter box but can't figure this out for the life of me.. Could anyone provide me with an example?

Thanks!

Did you read the following article? I hope this should resolve your issue.
www.trisul.org/docs/ug/alerts/tca.html

The above article has an example with the "Target Key" parameter as shown below:

TargetKey The key within the target counter group on which you want to create a TCA. You can enter this in either human readable format eg:Port-80, 192.168.1.33 or in Trisul key format: p-0050, C0.A8.00.01