Nested Sets and custom sorting

I'm having a problem with Joe Celko's nested set model for hierarchies combined with custom sorting. My ultimate goal is to generate a dhtml navigation menu based on a table in a sql server 2000 database. The main columns of this table are:

CREATE TABLE [dbo].[Contents] (

[Nr] [int] IDENTITY (1, 1) NOT NULL ,
[Parent] [int] NULL ,
[Hidden] [bit] NOT NULL ,
[Title] [varchar] (150) NOT NULL ,
[ListOrder] [varchar] (50) NULL ,
[ShowFrom] [datetime] NULL ,
[ShowUntil] [datetime] NULL ,
[SortIndex] [smallint] NOT NULL ,
[Folder] [bit] NOT NULL)

GO

Where
Nr: id of the item
Parent: the parent of the item
Hidden: indicates whether to show the item or not Title: the name of the item
Listorder: a string representing the way of sorting of the children of the items, eg ‘alphabetic', ‘defaul', ‘date' or ‘custom'. ShowFrom: the date the item should be shown from ShowUntil: the date the item should be shown until SortIndex: an integer indicating the sortorder in case parent.listorder = ‘custom'.
Folder: indicates whether the item can contain subitems/children.

The table contains about 1000 items at this time and I don't expect it to grow beyond 2000. Because the structure of this table is dictated by the vendor of the software (a content management solution), I can not make any changes to this table. So what I thought I would do is to fully re-populate/re-generate another table a couple of times a day using the nested sets model. This table would look like:

CREATE TABLE MyMenu (

	Nr INTEGER NOT NULL,
	Title VARCHAR (150) NOT NULL,
	lft INTEGER,
	rgt INTEGER,
	level INTEGER)