Keeping track of portfolio transactions on a FIFO basis

Assuming I would like to track my Apple holdings over time, automatically recording both realised and unrealised gains above and based on a FIFO accounting method, is there a way I could automatically update the corresponding BUY and SELL transaction records with the realised gains/loss whenever a new SELL transaction record is entered in the sequence ? How get I get this to work with Numbers spreadsheet given that it has no built-in macros ? Appreciate the help. Thanks.