Need help regards New Column Showing Highest Number seen from another cell calculated by a formula

Hello everyone,

I am a stock trader and using this magical StackBy in my day to day job to complete and organise my daily tasks,

Im running a stock return spreadsheet and have zapier updating the current price on one column. I then calculate the difference that I bought the stock at vs the current price. I want to add another column that watches for the highest return I have had and the percent return. Is there an if statement that can be watching the price difference and only change the cell if its higher than the previous high I’ve had?

Example. I buy a stock for $10 its now at $15. The net profit is $5. My highest return column shows $5. Tomorrow the stock goes to $20, the highest return column now shows $10 because its higher than the $5.