Maybe, this one is easy.
But somehow, I cannot find the proper information on this.
I would like to offer a form to my customers where they can delete post attachments. For this, I have inserted a pre-populated dropdown field where the posts are listed the current user has author rights on. Now, depending on the selection in the dropdown, they should be offered a field of checkboxes with the attachements of the just selected post. This is before submission of the form.
Is there a filter or hook to notify me when useres are changing selection in a pre-submission form? In fact, it is not even pre-submission because the user is not done making changes. Or do I have to scan the dropdown choices in the $Formobject for changes? What hook/filter could be used for that?