If you create a binding that passes data to, or retrieves data from, a data service, then you must create an event handler that calls the data service. A component can call a data service such as a web service only in response to an event. Otherwise, the data service is never invoked. You can create this event handler rapidly with Flex Builder.
The binding must appear in the Bindings panel (Window > Bindings). For more information, see Working with Flex data services.
For example, you can select a Button component for users to click.
A lightning bolt icon appears next to the field.
The Select Source for send() dialog box appears.
For example, if you want to invoke a weather-related web service, select the web service in the left pane (you must define the web service in the Data panel first) and then select the operation to invoke in the right pane.