Action or Campaign triggered by *second* application of same tag to contact

I need to create an action or a campaign that is triggered once a specific tag is applied to a contact for the second time.

More specifically, I need an email to be sent to a colleague when a contact receives a tag for the second time. I work for an online publication, and we want to be notified of the contacts that are featured twice on our blog. They receive their first tag thanks to Zapier - now I want Keap to send an email announcing the second publication of a contact.

I can’t seem to find this as a trigger - any workarounds?