Keeping the design of 2 tables in sync - sql-server

Question

The problem:
I have 2 tables in a database:
TableA TableB
X, Y, Z X, Y, Z
If I add column W to table A I want to copy it automatically to Table B with the same name and data type (without writing it explicitly).
Constraints on deployment:
The tables are updated using update scripts (so must be able to be called / executed in tsql).
There are multiple tables that could be updated (however I can hand code a mapping if needed)
Example update script:
IF NOT EXISTS (SELECT 1 FROM SYS.COLUMNS C INNER JOIN SYS.TABLES T ON C.OBJECT_ID = T.OBJECT_ID
WHERE C.NAME = 'W' AND T.NAME = 'TableA')
BEGIN
ALTER TABLE TableA ADD W [Int] NULL
END
GO
At the end of this script I want to add my ‘SyncMyTables’ SQL
So far from my research I have found 3 possible ways to tackle this:
Call a function at the end of the script which syncs the table designs
Some form of table trigger (but I don’t think triggers are that clever)
Some inline sql that builds up an update string and then runs it against the database.
Option 1 seems the most sensible to me.
What help I need:
Some guidance on how best to tackle this.
An example to point me in the right direction.
Cheers
please note, I don't want to keep the content of the columns in sync, I need to keep the table DESIGN

Answer 1

The column duplication can be achieved with a DDL trigger:
CREATE TRIGGER DDL_TableA_TableB
ON database
FOR ALTER_TABLE
AS
BEGIN
Declare #CommandText nvarchar(1000)
SELECT #CommandText = EVENTDATA().value('(/EVENT_INSTANCE/TSQLCommand/CommandText)[1]','SYSNAME');
if left(#CommandText, 26) = 'ALTER TABLE dbo.TableA ADD'
begin
set #CommandText = replace( #CommandText, 'TableA', 'TableB')
exec sp_executesql #CommandText
end
end