Drupal 7 Customize Node Add Form First, let's describe what I have already:


Vocabulary: "Categories" with some terms added(cat1, cat2, cat3) 
New content type "custom_page" where I added a new field of type "Term reference" using vocabulary "Categories"; 
Widget type for previous field is "Check boxes/radio buttons" because a custom_page can be part of multiple categories;


It is possible when adding a new custom_page, to add additional fields for each category selected?

Assuming, I checked "cat1" and "cat3" -> it is possible to add 3 more fields inline (new_field1, new_field2, new_field3) with every category selected?

Thanks,
Alex
Can't do with core functionality. You need to modify form using hook_form_alter. Probably you would want to use Drupal form's AJAX to make fields appear.

I don't know if there is a contrib module to do this, I can't see any.