Amazon MWS Marking order as shipped

I have listed all of my Amazon orders to my site.
Now, i want to have ability to mark order as shipped from my site and the status will be instantly updated on amazon.
I have looked at amazon feed api but not clear about the format of feed xml.
I just want an example feed xml for updating order status.
( actually i want to know which parameters in xml feed should i send to mark order status as shipped.)
Thanks in advance.