Craig,
I'm not super familiar with Target's audience creation capabilities, however, I believe this could be done via an Analytics shared segment.
Are you familiar with the People Core Service? It's also sometimes called Shared Audiences, Profiles & Audiences, or P&A.
Using the People Core Service, you should be able to create an Analytics segment containing the desired audience and share that with the Marketing Cloud. Target can then pick up on that audience for use in an experience. Unfortunately, Analytics shared audiences are subject to a 24-48 delay so I'm not sure if it would work for your use case?
Let me know if you'd like to discuss more.
Thanks,
Jantzen