MultiRow Alert to check the number of new clients in my application

We are using cloudwatch logs as the data source for grafana. We have users that register in our application. Each user is related to a client. We have created a panel that show us the number of users that has been registeered in the application in one month:
Client 1: 300 new users
Client 2: 456 new users

Then, we want to create an alert for all of our clients. The alert must loop over the clients and check if there aren’t new users registered. The alert should be check each 12 hours.

The client {{name of client}} hasn’t received any new users in the past 12 hours.

I am the only member of the Grafana team. We use Amazon Grafana.

We don’t know how to approach this issue. We have read the alerting documentation but we found no solution in there