SELECT 
	p.EmpId, 
	p.ModuleID, 
	StartDate = 
		CASE 
			WHEN p.ModuleID = 5 AND t.StartDate IS NOT NULL THEN t.StartDate
			ELSE p.StartDate
		END, 
	CompleteDate =
		CASE 
			WHEN p.ModuleID = 5 AND t.CompleteDate IS NOT NULL THEN t.CompleteDate
			ELSE p.CompleteDate
		END
FROM t_ParticipantStatus p
LEFT OUTER JOIN
(
	SELECT EmpID, StartDate, CompleteDate
	FROM t_ParticipantStatus
	WHERE ModuleID = '1' AND CompleteDate > '10/1/05'
) t
ON p.EmpId = t.EmpId

CREATE TABLE t_ParticipantStatus
(
	EmpID int,
	ModuleID char(1),
	StartDate datetime,
	CompleteDate datetime
)

INSERT INTO t_ParticipantStatus VALUES(66, '1', '10/1/05', '10/10/05')
INSERT INTO t_ParticipantStatus VALUES(77, '1', '10/6/05', '10/8/05')
INSERT INTO t_ParticipantStatus VALUES(99, '1', '9/1/05', '9/3/05')
INSERT INTO t_ParticipantStatus (EmpId, ModuleID) VALUES(66, '5')
INSERT INTO t_ParticipantStatus (EmpId, ModuleID) VALUES(99, '7')

SELECT *
FROM t_ParticipantStatus

SELECT 
	p.EmpId, 
	p.ModuleID, 
	StartDate = 
		CASE 
			WHEN p.ModuleID = 5 AND t.StartDate IS NOT NULL THEN t.StartDate
			ELSE p.StartDate
		END, 
	CompleteDate =
		CASE 
			WHEN p.ModuleID = 5 AND t.CompleteDate IS NOT NULL THEN t.CompleteDate
			ELSE p.CompleteDate
		END
FROM t_ParticipantStatus p
LEFT OUTER JOIN
(
	SELECT EmpID, StartDate, CompleteDate
	FROM t_ParticipantStatus
	WHERE ModuleID = '1' AND CompleteDate > '10/1/05'
) t
ON p.EmpId = t.EmpId

DROP TABLE t_ParticipantStatus

UPDATE p
SET
	StartDate = 
		CASE 
			WHEN p.ModuleID = 5 AND t.StartDate IS NOT NULL THEN t.StartDate
			ELSE p.StartDate
		END, 
	CompleteDate =
		CASE 
			WHEN p.ModuleID = 5 AND t.CompleteDate IS NOT NULL THEN t.CompleteDate
			ELSE p.CompleteDate
		END
FROM t_ParticipantStatus p
LEFT OUTER JOIN
(
	SELECT EmpID, StartDate, CompleteDate
	FROM t_ParticipantStatus
	WHERE ModuleID = '1' AND CompleteDate > '10/1/05'
) t
ON p.EmpId = t.EmpId