Restoring A Default Constraint

Troops,

I'm a software developer trying to hack my way thru a SQL script to increase the size of a column. The column has a constraint on it that won't allow the alter unless its dropped.

Alter command:
ALTER TABLE dbo.QueueBack ALTER Column QBQueue varchar(4) NOT NULL

Message response:
Msg 5074, Level 16, State 1, Line 10
The object 'DF__QueueBack__QBQue__76818E95' is dependent on column 'QBQueue'.
Msg 4922, Level 16, State 9, Line 10
ALTER TABLE ALTER COLUMN QBQueue failed because one or more objects access this column.


So, my script drops the default constraint, alters the column size and then adds the constraint back. The problem is that the constraint does NOT appear to be the same as it was prior. I can run the Alter command on the column and it will allow me to change the size of the column... where it prohibited me from doing such before. How do I restore the default constraint so it is exactly the way it was before I dropped it?

Thx,

Stretch

---------------------------------

Script for drop, alter, add... modified slightly for simplicity...

declare @Error int

BEGIN TRAN
SELECT @Error = 0

DECLARE @defname VARCHAR(100), @cmd VARCHAR(1000)

-- this is retrieved at run time from the sysconstraints table; hard-coded here...
set @defname = 'DF__QueueBack__QBCategory'

IF @defname <> ''
BEGIN
SET @cmd = 'ALTER TABLE dbo.QueueBack DROP CONSTRAINT '+ @defname
EXEC(@cmd)

if @@ERROR = -1
BEGIN
SET @Error = -1
END
END

if @Error = 0
BEGIN
-- modify the column
ALTER TABLE dbo.QueueBack ALTER Column QBCategory varchar(7) NOT NULL

if @@ERROR = -1
BEGIN
SET @Error = -1
END
END

if @Error = 0
BEGIN
-- Add the default constraint back
SET @cmd = 'ALTER TABLE dbo.QueueBack ADD CONSTRAINT '+ @defname + ' DEFAULT ('''') FOR QBCategory'
EXEC(@cmd)

if @@ERROR = -1
BEGIN
SET @Error = -1
END
END


if @Error = 0
BEGIN
-- Commit if no error...
COMMIT TRAN
END
ELSE
BEGIN
-- Rollback if error...
ROLLBACK TRAN
END

GO