How can I calculate realised profits/loss after each Sell trade date?

I created a portfolio for tracking my investments.

I did up most of it already, but I can't seem to think of a way to calculate Net Profits/Loss after each Sell.
Hence I can't make a chart that makes sense.

1) How can I calculate each Profit/Loss after I sell either partial or all the stocks?

2) So that I can Chart based on every SELL date, and the profit/loss affects the original balance, and the chart will make more sense.

Thanks for reading!