Summary Report Of Shares Bought And Sold

A worksheet called "purchases" contains the list of shares purchased during the period 1.4.5 to 31.3.8. It has four columns :

1. Date
2. Name of the share (name is repeated for every new purchase as it is entered in a new row and is totally independent of the earlier entry of purchase)
3. Qty
4. Sale price

Likewise there is a sheet for sales also. I want to do the following:

a) Find out all the records showing purchases of a particular share and add them up (both quantity and value). And thus, make a list of shares showing aggregate purchase of each share during the entire year. Likewise, I want to do this for sales also.

b) For every share that has been sold within one year after its purchase, apply 20% tax on the profit earned on sale of such share.

Additional information: If 100 shares of A Ltd are purchased on 1.4.5 and 200 shares on 1.5.5 then during the sale of 150 shares of A Ltd on 2.4.6, 100 shares purchased on 1.4.5 and 50 shares purchased on 1.5.5 shall be deemed to have been sold.