What is the query that updates the Column in a table
sys.sql_modules isn't going to help you - you won't know which one is causing a specific update, or who's calling it. Here's a start - create a logging table:

CREATE TABLE dbo.UpdateLog
(
  EventType  SYSNAME,
  Parameters INT,
  EventInfo  NVARCHAR(MAX),
  EventDate  DATETIME NOT NULL DEFAULT GETDATE(),
  AppName    SYSNAME  NOT NULL DEFAULT APP_NAME(),
  HostName   SYSNAME  NOT NULL DEFAULT HOST_NAME(),
  LoginName  SYSNAME  NOT NULL DEFAULT SUSER_SNAME()
);


Then create a trigger for updates to the source table:

CREATE TRIGGER dbo.tr_whatever
ON dbo.whatever
WITH EXECUTE AS OWNER
AFTER UPDATE
AS
BEGIN
  SET NOCOUNT ON;
  IF EXISTS 
  (
    SELECT 1 FROM inserted AS i
      INNER JOIN deleted AS d
      ON i.id = d.id -- use key column(s) here
      AND i.x &lt;&gt; d.x -- assumes column x is not nullable
  )
  BEGIN
    INSERT dbo.UpdateLog(EventType, Parameters, EventInfo)
      EXEC sys.sp_executesql N'DBCC INPUTBUFFER(@@SPID) WITH NO_INFOMSGS;'; 
  END
END
GO


Now you'll be able to see not only what query fired the trigger, but also who ran it, when, and from which application.