Need Modifications to UDF Code to handle multiple Inventory on the same Sheet

Hi,
Can someone review the attached Excel Spreadsheet I found here: http://www.excelforum.com/excel-gene...book-cost.html , and in particular, the UDF code contained therein which support the FIFO Cost of Sales calculation in Column H on Sheet1.

Once reviewed, could you please modify the UDF code to support multiple stocks on one sheet as shown in the Sheet2 sample? Sheet2 uses the same UDF calls , but it does not calculate correctly if there are different stocks (shown in Column C) on the same sheet. Again, Column H shows the use of the UDF calculating the Cost of Sales.

It appears that the UDF code only supports one (1) stock at a time as shown in Sheet 1. This means that if you have say, 20 stocks, you'll have to have 20 sheets. I'm interested in it supporting multiple stocks on one sheet as shown in Sheet2; but with correct calculations.

Any help is very much appreciated.

Thanks.