Formula to calculate loss
 

I have a worksheet where I have the following columns: INVOICENUMBER, TYPE,
INVOICEDATE, BILL-TO, COSTCENTER, PRACTICENAME, ADDRESS, CITY, STATE, ZIP,
MFGNO, MANUFACTURER, DESCRIPTION, ITEMNO, UNIT, QTYSHIP, UNITPRICE, AMOUNT.
I have tried several different approaches to manipulate this data. Now I
want to see if there is a way to say... If the manufacturer, description, &
mfg # match, take the lowest unit price and multiply that by the sum of the
quanitity then subtract that from what the actual total of the amount spent
(sum of amount) and the result would be the loss of $$ due to purchasing at
those higher prices. How can I do this... even if it is not all in one
formula, there has to be a way.

--
Thank you very much for your help!!! I really appreciate it :o).