add_filter('gform_pre_render', 'disable_submit');
 
function disable_submit($form) {
	?>
	<script type="text/javascript">
	jQuery(document).ready(function($){
		$('#gform_submit_button').on('click', function(event){		    
			var submitCopy = $(this).clone();
			submitCopy.prop('id', '').prop('disabled', true).prop('value', 'Processing...').insertAfter($(this));
			$(this).hide();
		});
	});
	</script>
	<?php
	return $form;
}
//javascript/8235