To run a pipeline that retrains a machine learning model based on a trigger from an external system, you can use Azure Logic App. Azure Logic App is an event-driven platform that can be used to trigger applications, processes, or CI/CD workflows based on Azure Machine Learning events. You can set up a Logic App to be triggered by a Machine Learning event, such as a pipeline run, and then perform an action based on that trigger.
https://learn.microsoft.com/en-us/azure/machine-learning/how-to-use-event-grid?view=azureml- api-2