Alert RegEx Question

[EthanKC]

I'm trying to set up alerts on a feed, so they only alert for ACK messages (I got that figured out), but they don't alert for ACKs if the original message was for a particular study description. I figured out the regex for the ACK portion, but the ACK messages we're receiving don't reference the study description at all. Is there any way with alerts to look back at the message that generated the alert, and have the system filter based on that message?