-- Sequence table, holds next PK per table
CREATE  TABLE dbo.GPK
        (
        table_name  SYSNAME NOT NULL PRIMARY KEY,
        next_value  INTEGER NOT NULL
        );
GO
-- Example row
INSERT  dbo.GPK (table_name, next_value) VALUES (N'dbo.MyTable', 0);
GO
-- Procedure to allocate a new PK
CREATE PROCEDURE dbo.usp_GenPK(@table_name SYSNAME, @NewID INT OUTPUT)
AS 
BEGIN 
        UPDATE  dbo.GPK 
        SET     @NewID = next_value = next_value + 1 
        WHERE   table_name = @table_name;
END;
GO
-- Test
DECLARE @NewID INTEGER;
EXEC    dbo.usp_GenPK N'dbo.MyTable', @NewID OUTPUT;
SELECT  @NewID;

BEGIN TRAN
EXEC    dbo.usp_GenPK N'dbo.MyTable', @NewID OUTPUT;
WAITFOR DELAY '00:02';
COMMIT