SQL Server 2008 :: Retrieving Same Identity Column Value By Multiple Users

I am using following queries in a stored procedure.This stored procedure is executed through a dot net application.

DECLARE @DEPTNBR BIGINT
SELECT @DEPTNBR = DEPTNBR
FROM DEPARTMENT_DETAILS WITH (UPDLOCK,READPAST)
WHERE STATUS= 1
UPDATE DEPARTMENT_DETAILS SET STATUS= 0 WHERE DEPTNBR = @DEPTNBR
SELECT DEPTNBR,DEPTNAME,DEPTLOC FROM DEPARTMENT_DETAILS WHERE DEPTNBR = @DEPTNBR ​

From my queries,I am providing a available department information.Each user needs to get unique available department information.But when more number of users using the application concurrently, multiple users getting same department information.How to solve my problem?I always wants to get unique department information even though multiple users using the application concurrently.