I agree, not sure why you would ever want the same data in another column; maybe you should make it null or add a placeholder, and then do some calculation and populate later?
You might do something like this?
DROP TABLE #example
GO
CREATE TABLE #example(exampleId int identity(1,1) NOT NULL PRIMARY KEY,
exampletext varchar(30),
myCalculatedField AS SUBSTRING (ExampleText, CHARINDEX(':', exampleText )+1, len(exampleText)),
myCalcd2 AS UPPER(LEFT(SUBSTRING (ExampleText, CHARINDEX(':', exampleText )+1, len(exampleText)),4))
)
GO
INSERT INTO #example (exampletext)
VALUES ('Product Description: Chair' )
GO
SELECT * FROM #example
GO