droping a CONSTRAINT

I am having problem to find the right syntax to DROP a column with contrainst and recrate it
I get an error

if exists ( select * from INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME='myTable'
and COLUMN_NAME='myDate' )
ALTER TABLE [dbo].[myTable] DROP COLUMN myDate
GO

ALTER TABLE [dbo].[myTable] WITH NOCHECK ADD
myDate datetime CONSTRAINT [DF_myDate] DEFAULT (GetDate())
GO

Query Analyser says :
Server: Msg 5074, Level 16, State 1, Line 5
The object 'DF_myDate' is dependent on column 'myDate'.
Server: Msg 4922, Level 16, State 1, Line 5
ALTER TABLE DROP COLUMN myDate failed because one or more objects access this column.
Server: Msg 2705, Level 16, State 4, Line 2
Column names in each table must be unique. Column name 'myDate' in table 'dbo.myTable' is specified more than once.

thank you for helpingYou do know that the first statement failed, and since it was isolated in it's own batch by the GO, the second statement tried to run. So that's uderstandable, since the column did not drop, you can't re-add it.

Do this, go in to Enterprise Manager, right click on the table and chose design make your changes, DON'T SAVE them, and click on the save script icon

It will show you exactly what to do|||I get an incredible script !!

I really dont understant
here I dop the column

if exists ( select * from INFORMATION_SCHEMA.COLUMNS
where TABLE_NAME='myTable'
and COLUMN_NAME='myDate' )
ALTER TABLE [dbo].[myTable] DROP COLUMN myDate
GO

then it doesnt exist any more ! why I cannot create it after ?|||because u failed to drop it....... u got error message :
Server: Msg 5074, Level 16, State 1, Line 5
The object 'DF_myDate' is dependent on column 'myDate'.
Server: Msg 4922, Level 16, State 1, Line 5
ALTER TABLE DROP COLUMN myDate failed because one or more objects access this column.

u cant drop the column, coz it has constraint 'DF_myDate'. drop the constraint first, then drop the column, then create the column with constraint again.