what formulas will give correct results
 

I have a in Col A date range in ascending,non-contiguous order.In Col B
"Open Price",in Col c "high price",In Col C "Low price",In Col D "Close
Price" of a commodity.My questions
1.In last 15 days on which date the commodity quoted(or reached) highest
price?
2.In last 15 days what is the highest price, and its cell adresss?
(remember the above date range the prices may be similar in different dates)
3.If I bought the commodity on any date in above range in certain rate
(say on 02/02/07 at Rs.25.50) ,what would have been best sell date in
the above date range? ( Average of open,high,low and colse price is the best
price of the day,highest of best average price on any day after the purchase
date is best sell price and the date is best sell date)