Self Join with Randomisation too slow

Hi,

I have a query which run thousand of times within the loop with randomised data.  Basically, the loop randomises the data/column on each iteration and then performs some calculations.  The below query is what I came up with but it takes too slow when compared with non-randomised way.  I have commented out the line with non-randomisation, which joins to the same row_numbers.  The table only contains about few thousand rows.  Is there a way to re-structure the randomisation to speed up ?

WHILE @counter <= 10
	BEGIN
		--Some SELECT Queries eliminated for clarity

		--Randomise and Delete temp tables
		DELETE @tmpReCalcBloomberg
		DELETE @tmpAnniversaryTemp
		UPDATE @tmpBloomberg
		SET randomNo = FlOOR(RAND(CHECKSUM(NEWID())) * (@upperNO-@lowerNO)+@lowerNO)

		--Randomise Returns AND Calculate Prev products
		INSERT INTO @tmpReCalcBloomberg
		SELECT b2.bl_date, b2.bl_rowNo, b1.bl_rowNo, b1.bl_und1, b1.bl_und2, b1.bl_und3, b1.bl_und4, b1.bl_und5, 
			ROUND(EXP(SUM(LOG(b1.bl_und1)) OVER(ORDER BY b2.bl_rowNo)), 17),
			ROUND(EXP(SUM(LOG(b1.bl_und2)) OVER(ORDER BY b2.bl_rowNo)), 17),
			ROUND(EXP(SUM(LOG(b1.bl_und3)) OVER(ORDER BY b2.bl_rowNo)), 17),
			ROUND(EXP(SUM(LOG(b1.bl_und4)) OVER(ORDER BY b2.bl_rowNo)), 17),
			ROUND(EXP(SUM(LOG(b1.bl_und5)) OVER(ORDER BY b2.bl_rowNo)), 17)
		--FROM @tmpBloomberg AS b1 JOIN @tmpBloomberg AS b2 ON b1.bl_rowNo = b2.bl_rowNo
		FROM @tmpBloomberg AS b1 JOIN @tmpBloomberg AS b2 ON b1.bl_rowNo = b2.randomNo

		SET @counter = @counter + 1
	END