How to increment Row value(Running Number) in sql server

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SQL-server-2000

SQL-Server

SET QUOTED_IDENTIFIER ON 
GO
SET ANSI_NULLS ON 
GO

ALTER TRIGGER [PIP_ENTRYINSERT]  ON dbo.PIP_Entry
   
	AFTER INSERT AS 
	
	UPDATE PIP_ENTRY SET pipcode = (SELECT 'PIP'++CONVERT(VARCHAR,MAX(pipcode1)+1) FROM PIP_ENTRY) where pipcode =''
	UPDATE PIP_ENTRY SET pipcode1 = (SELECT MAX(pipcode1)+1 FROM PIP_ENTRY) where pipcode1 = 0

GO
SET QUOTED_IDENTIFIER OFF 
GO
SET ANSI_NULLS ON 
GO

The Above trigger i have used to increment row value when ever data is inserted (ie., After insert trigger). Here i have a problem when i use this trigger in web application. The actual problem is number of user's inserting data at same time then it is not working it is not able to generate running number for all the users. Because this trigger works like row-identity.
So i need solution for this post.
Thanks in advance