Listening to a widget directly from a microflow (unless the microflow is triggered by the widget) is not possible. However your widget is able to listen to changes in objects. Via the mx.data.subscribe() function in the mxui api. Which means that everytime you change and refresh an object the subscribed widgets will be notified and the function that was set as the handler will be triggered.
When using this make sure you also unsubscribe when destroying the widget.