如何在SQL Server 2005数据库中使用T-SQL使用零填充NVARCHAR字段？

I have an Orders table that stores the Ordernumber as NVarChar. We manually increment the order number by querying for the biggest order number ordering in descending order and returning the top 1 and then adding 1. We have this implemented in Microsoft CRM 4.0.I have an Orders table that stores the Ordernum