The LiveCycle Cookbook, a community resource for developers, has a recent recipe and sample artifact by Arjun V: Toggling between two fields in a dynamic form.

The Cookbook homepage is here: http://cookbooks.adobe.com/livecycle. Check out the available recipes and contribute your own.

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Original article at http://blogs.adobe.com/samartha/2012/03/toggling-between-two-fields-in-a-dynamic-form.html.