Embedding renderable forms api Is there any way to embed form fields (i.e. textfield) within other field (i.e. radios). I'd like to create something like radiobuttons list: first default and second (if selected) allow user to enter text value. 
Maybe I should create custom compound cck field?
This module may help: Select (or other)

Or maybe you want use form alter and #state attribute: http://api.drupal.org/api/drupal/developer!topics!forms_api_reference.html/7#states