Stock P/L technique

[Don]

I'm trying to keep track of my stock trades profit and loss (P/L) using the
standard first in, first out accounting method (FIFO). As I buy stocks
naturally I record the purchase price in my Excel spreadsheet. Sometimes I
buy the same stock in several batches over time and my problem is that when
I sell the stock I need to calculate the P/L using the oldest prices first.
Then those old prices need to be somehow ignored and as subsequent sells
occur the next oldest remaining prices need to be used to calculate P/L.

I have no clue how to keep track of the "buy prices" previously used for P/L
versus those that are unused. I'm hoping there is a way to keep track
without having to write VBA routines.

Can anybody provide some ideas using standard Excel formulas? Although I
guess I can cope with some real simple VBA routines if I have to.

Thanks
Don