Aggregate using the same set

I am trying to aggregate on the set itself on the basis of intra day amount happening. 
May be below query will help you understand my requirement more 

SELECT B.time, B.date, B.att1, SUM(A.COST)
FROM TBL1 B, TBL1 A
WHERE  A.time <= B.time
AND A.DATE = B.DATE AND A.att1 = B.att1
GROUP BY A.att1,A.att2,A.time, A.date;

I am not able to achieve it with any operator or multiple operators. Can anyone help me out on this.