StdWebContainerMessageReceived event
When this event is triggered, it populates the form variables StdWebPageMessageContext and StdWebPageMessageData with the message values that were set by an event handler with response type Send Web Container Message.
Example
You want a form on the child frame to update an edit box with a value from the main frame.
Generate the Send Web Container message event from the main frame with a message type of sendMessageToContainer. The "JSON data" contains setComponent=editBoxA, toValue=V(valueToSend). (The data that is defined here is up to the form developer.)
On the child form, use the event handler StdWebContainerMessageReceived. Parse ThisForm.Variables(StdWebPageMessageData) to retrieve the values of setComponent and toValue. Then use a form script to set the value to the component.