Create an excel logic to lock my profit from selling shares

In this example column B is the closing price of a stock. My initial investment is $10,000
I would like to take profit when the stock is up only by the 50%. In this example on 1/4/2023 I would like to sell fraction of shares to get $77.20/2 = $38.61 in cash
Then the next day if market is down then ONLY I would like to buy more shares with $38.61 otherwise I'll keep cash.
If my portfolio value is down from $10,000 I'll not do anything. I would like to generate revenue by selling little bit, no additional cash will come from other sources.

How can I create this kind of logic to know my portfolio value at today's date?

Please see the sample excel file.