for example
if(!vmAccess::manager('core') ){
$msg = 'Forget IT';
$this->setRedirect('index.php?option=com_virtuemart', $msg);
}
Redirects any non Superadmin. Or use only vmAcess::manager(), checks for managers ('core.admin', 'core.manage', 'vm.manage'), which is usually the standard. You can also check for a certain right. The rights to check orders would be 'orders' => vmAccess::manager('orders') and only for order status change it is 'orders.status'. You can even check for more than one right and chain it or use it as or.
I just notice the right order.status is atm only used in the controllers, so it is not checked in your case.
It automatically checks also for Background admin rights. ;-) Makes fun