Web service call to fetch orders from Commerce Server 2007

Here is an exmaple of a web service call to search for orders in Commerce Server:

            System.Xml.XmlDocument searchClause = new System.Xml.XmlDocument();
            searchClause.LoadXml(@"<CLAUSE OPER=""equal"" xmlns=""http://schemas.microsoft.com/CommerceServer/2004/02/Expressions"">
    <PROPERTY ID=""PurchaseOrder.Status"" MULTIVAL=""false"" TYPE=""String"" />
    <IMMED-VAL TYPE=""String"">
      <VALUE>NewOrder</VALUE>
    </IMMED-VAL>
  </CLAUSE>");
            SearchOptions searchOptions = null;
            OrderService os = new OrderService();
            os.Credentials = new System.Net.NetworkCredential("User", "Password", "domain");
            DataSet ds = os.GetAllowedStatus();
            ds = os.SearchPurchaseOrders((System.Xml.XmlElement)searchClause.FirstChild, searchOptions);