My scenario looks as follow: I have a form element of checkboxes, e.g. 3. If the rightmost checkbox is marked, the other 2 are greyed out and so on. I don't know how to do this, because if I use the #disabled property all of them are greyed out.
I thought about to make several single checkboxes of type #checkbox and use an ajax call and look at the $form_state and rerender all of them as single ones (disable them then etc.). But there is a problem that I use a form in a drupal block, and I haven't got the &$form_state as a parameter of the function.
What is the best method to do this?