Index: modules/in-commerce/units/orders/orders_event_handler.php
===================================================================
--- modules/in-commerce/units/orders/orders_event_handler.php
+++ modules/in-commerce/units/orders/orders_event_handler.php
@@ -66,7 +66,7 @@
 						return false;
 					}
 
-					if ( $event->Name == 'OnUpdate' ) {
+					if ( substr($event->Name, 0, 8) == 'OnUpdate' ) {
 						// all checks were ok -> it's user's order -> allow to modify
 						return true;
 					}
@@ -128,6 +128,7 @@
 			'OnSelectAddress'		=>	Array('self' => true),
 			'OnProceedToBilling'	=>	Array('self' => true),
 			'OnProceedToPreview'	=>	Array('self' => true),
+			'OnProceedToPreviewAjax' => array('self' => true),
 			'OnCompleteOrder'		=>	Array('self' => true),
 			'OnUpdateAjax'			=>	Array('self' => true),
 
@@ -4043,13 +4044,31 @@
 	/**
 	 * Performs order update and returns results in format, needed by FormManager
 	 *
-	 * @param kEvent $event
+	 * @param kEvent $event Event.
+	 *
+	 * @return void
 	 */
-	function OnUpdateAjax($event)
+	protected function OnUpdateAjax(kEvent &$event)
 	{
-		$ajax_form_helper = $this->Application->recallObject('AjaxFormHelper');
+		$ajax_form_helper =& $this->Application->recallObject('AjaxFormHelper');
 		/* @var $ajax_form_helper AjaxFormHelper */
 
 		$ajax_form_helper->transitEvent($event, 'OnUpdate');
 	}
+
+	/**
+	 * Performs order update after billing step submission and returns results in format, needed by FormManager
+	 *
+	 * @param kEvent $event Event.
+	 *
+	 * @return void
+	 */
+	protected function OnProceedToPreviewAjax(kEvent &$event)
+	{
+		$ajax_form_helper =& $this->Application->recallObject('AjaxFormHelper');
+		/* @var $ajax_form_helper AjaxFormHelper */
+
+		$ajax_form_helper->transitEvent($event, 'OnProceedToPreview');
+	}
+
 }