Webform modullal előállított űrlap feltételhez kötött beküldése

Pont most olvastam a Pro drupal 7 development című könyvben az erre vonatkozó részt. Mondjuk saját példamodult írt a szerző, de talán segít. Itt az ide vonatkozó rész:

Validating User-Submitted Settings
If system_settings_form() is taking care of saving the form values for us, how can we check whether the
value entered in the “Annotations per node” field is actually a number? We just need to add the check to
see whether the value is numeric to a validation function (annotate_admin_settings_
validate($form, $form_state)) in sites/all/modules/custom/annotate/annotate.admin.inc and use it to
set an error if we find anything wrong.
/**
* Validate annotation settings submission.
*/
function annotate_admin_settings_validate($form, &$form_state) {
$limit = $form_state['values']['annotate_limit_per_node'];
if (!is_numeric($limit)) {
form_set_error('annotate_limit_per_node', t('Please enter number.'));
}
}
Now when Drupal processes the form, it will call back to annotate_admin_settings_validate() for
validation. If we determine that a bad value has been entered, we set an error against the field where the
error occurred, and this is reflected on the screen in a warning message and by highlighting the field
containing the error.
How did Drupal know to call our function? We named it in a special way, using the name of the form
definition function (annotate_admin_settings) plus _validate. For a full explanation of how Drupal
determines which form validation function to call, see Chapter 11.

Találtam egy olyan modult, hogy terms of use, talán az is megoldja a problémád:

http://drupal.org/project/terms_of_use