There are often cases when a page requires some type of interaction with one or more of its regions. If the interaction depends on application data being shared between the two, typically either input parameters or a <data-control-scope> of "shared" is utilized by the region. If only a small payload of application data is to be shared without restarting the region, contextual framework events can be used. But, when a page must initiate control flow navigation within one of its regions the best approach is to utilize the queueActionEventInRegion(...) method located within the oracle.adf.view.rich.component.rich.fragment.RichRegion class.
To help describe the required development approach, I've created a Initiate Control Flow Within Region From Its Parent Page pattern document available on OTN. It contains a link to download a sample application. The pattern document and sample application also describe how to use region capabilities to enable/disable buttons on the parent page based on the current state of the region. Just follow the recommended development approach. It's easy to navigate your way through it. :)
