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

Question

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