Alter Table Alter Column

I would like to add an Identity to an existing column in a table using a
stored procedure then add records to the table and then remove the identity
after the records have been added or something similar.
here is a rough idea of what the stored procedure should do. (I do not know
the syntax to accomplish this can anyone help or explain this?

Thanks much,

CBL




CREATE proc dbo.pts_ImportJobs
as

/* add identity to [BarCode Part#] */
alter table dbo.ItemTest
alter column [BarCode Part#] [int] IDENTITY(1, 1) NOT NULL

/* add records from text file here */

/* remove identity from BarCode Part#] */
alter table dbo.ItemTest
alter column [BarCode Part#] [int] NOT NULL
return

GO
SET QUOTED_IDENTIFIER OFF
GO
SET ANSI_NULLS ON
GO



here is the original table

CREATE TABLE [ItemTest] (
[BarCode Part#] [int] NOT NULL ,
[File Number] [nvarchar] (20) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
CONSTRAINT [DF_ItemTest_File Number] DEFAULT (''),
[Item Number] [nvarchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
CONSTRAINT [DF_ItemTest_Item Number] DEFAULT (''),
[Description] [nvarchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
CONSTRAINT [DF_ItemTest_Description] DEFAULT (''),
[Room Number] [nvarchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
CONSTRAINT [DF_ItemTest_Room Number] DEFAULT (''),
[Quantity] [int] NULL CONSTRAINT [DF_ItemTest_Quantity] DEFAULT (0),
[Label Printed Cnt] [int] NULL CONSTRAINT [DF_ItemTest_Label Printed Cnt]
DEFAULT (0),
[Rework] [bit] NULL CONSTRAINT [DF_ItemTest_Rework] DEFAULT (0),
[Rework Cnt] [int] NULL CONSTRAINT [DF_ItemTest_Rework Cnt] DEFAULT (0),
[Assembly Scan Cnt] [int] NULL CONSTRAINT [DF_ItemTest_Assembly Scan Cnt]
DEFAULT (0),
[BarCode Crate#] [int] NULL CONSTRAINT [DF_ItemTest_BarCode Crate#] DEFAULT
(0),
[Assembly Group#] [nvarchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
CONSTRAINT [DF_ItemTest_Assembly Group#] DEFAULT (''),
[Assembly Name] [nvarchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
CONSTRAINT [DF_ItemTest_Assembly Name] DEFAULT (''),
[Import Date] [datetime] NULL CONSTRAINT [DF_ItemTest_Import Date] DEFAULT
(getdate()),
CONSTRAINT [IX_ItemTest] UNIQUE NONCLUSTERED
(
[BarCode Part#]
) ON [PRIMARY]
) ON [PRIMARY]
GO