set @ProgID = 59

set @yearnum = 2007

set @QtrYearNum = 3


SELECT t.ProgID, t.taskid,isnull(avg(t.PctComplete),0),isnull(avg(t.award_amt),0), ISNULL(SUM(c.amount),0) 
	FROM TAB_ccsNetTasksLog t 
	INNER JOIN tab_ccsnetcostdetails c ON (t.TaskID = c.TaskID and c.EstimateType ='Final' and c.COexecuted = 1 AND t.ProgID=@ProgID)
	Inner Join tab_ccsnetco co on (c.coid = co.coid and c.coexecuted=1)
	Where
		CASE @QtrYearNum
			WHEN 1 THEN  month(t.PctCompleteDate)=1 or month(t.PctCompleteDate)=2 or month(t.PctCompleteDate)= 3 and year(t.PctCompleteDate) = @yearnum
			WHEN 2 THEN  month(t.PctCompleteDate)= 4 or month(t.PctCompleteDate)= 5 or month(t.PctCompleteDate)= 6 and year(t.PctCompleteDate) = @yearnum 
			WHEN 3 THEN  month(t.PctCompleteDate)= 7 or month(t.PctCompleteDate)= 8 or month(t.PctCompleteDate)= 9 and year(t.PctCompleteDate) = @yearnum
			WHEN 4 THEN  month(t.PctCompleteDate)=10 or month(t.PctCompleteDate)= 11 or month(t.PctCompleteDate)= 12 and year(t.PctCompleteDate) = @yearnum
		END
	GROUP BY t.ProgID, t.taskid, t.award_amt, t.Pctcomplete

....
Where  datepart(qq,t.PctCompleteDate) = @QtrYearNum and year(t.PctCompleteDate)=@YearNum
....

...
where t.PctCompleteDate > = DATEADD(qq,@QtrYearNum-1,DATEADD(yy,@YearNum-1900,0))
and t.PctCompleteDate < DATEADD(qq,@QtrYearNum,DATEADD(yy,@YearNum-1900,0))