Right, it doesn't work.

The trigger you gave me allows me to change rows one and five but I can't changes them back. Example

UPDATE TEST

SET col1 = 'one_test'

WHERE col1 = 'one'

(changes the row...

Thanks Jo, very simple and effective.

I changed the trigger to this and it worked great. 

CREATE TRIGGER TR_TEST_MANDATORY ON dbo.TEST for UPDATE, DELETE

AS

SET NOCOUNT ON

IF