I would write a stored procedure to do it: that way it is all done within the database, and there is no risk of other people doing the same thing, and you ending up with wrong values.
USE [myDatabase]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE procedure [proc_addtovals]
AS
UPDATE myTable SET column2=column2+1, column3=column3+4