Hello!
This kb article shows how to hide the next button in a multi page form.  
https://formidableforms.com/knowledgebase/javascript-examples/#kb-conditionally-hide-next-buttons-in-a-multi-page-form
My problem is I need to hide the next button if 2 fields are empty. These are hidden fields. Is there a way to meet this condition?
Thanks for any advise!

This is the script of the KB article: 

<script>
jQuery(document).ready(function($){
  var fieldID = 18;
  var showVal = 'Yes';
  var $nextButton = $(".frm_button_submit");

  //Hide next button by default if Yes is not already checked
  if (($("input[name^='item_meta[" + fieldID + "]']:checked").val() != showVal) && ($("input[type=hidden][name^='item_meta[" + fieldID + "]']").val() != showVal)) {
    $nextButton.css('visibility','hidden');
  }

  $("input[name^='item_meta[" + fieldID + "]']").change(function(){ 
    if ($("input[name^='item_meta[" + fieldID + "]']:checked").val() == showVal){
      $nextButton.css('visibility','visible');
    } else {
      $nextButton.css('visibility','hidden');
    }
  });
});
</script>