DECLARE @Sample Table(ACCT char(3), CurBal int, [Date] varchar(4))
INSERT INTO @Sample VALUES ('001',100,'day1'), ('002',90,'day1'), ('003',50,'day1'), ('001',80,'day2'), ('003',110,'day2'), ('004',100,'day2')

;WITH CTE AS(
	SELECT	
		*, 
		ROW_NUMBER() OVER (PARTITION BY ACCT ORDER BY [DATE]) RN
	FROM	@Sample
)
SELECT	
	a.ACCT, 
	CASE WHEN a.CurBal <> b.CurBal THEN b.CurBal ELSE a.CurBal END, 
	b.Date, 
	CASE WHEN a.CurBal < b.CurBal THEN a.CurBal WHEN b.CurBal < a.CurBal THEN b.CurBal ELSE a.CurBal END, 
	b.RN - a.RN + 1, 
	a.Date
FROM	CTE a
	CTE b
WHERE	a.ACCT = b.ACCT
	AND a.RN <= b.RN
	OUTER APPLY(
		SELECT	*
		FROM	CTE b
		WHERE	a.ACCT = b.ACCT
			AND a.RN <= b.RN)b
ORDER BY 3, 6, 1