This ProBuilder script is designed to track trading positions based on the Stochastic Oscillator, a popular momentum indicator. The code identifies entry and exit points for trades and calculates the profit or loss from these trades.

mystoch = Stochastic[10,3](close)
if not on and mystoch crosses under 20 then
    myopen = close
    on = 1
endif
if on and mystoch crosses over 80 then
    myclose = close
    diff = myclose - myopen
    on = 0
endif
return diff

Explanation of the Code:

• Initialization: The variable mystoch is assigned the value of the Stochastic Oscillator with parameters 10 for the period and 3 for the smoothing. It uses the closing price (close) of the stock or asset.
• Entry Condition: The script checks if the variable on is not active (false) and if the Stochastic value crosses below 20. This is typically considered an oversold condition, prompting a buy signal. If these conditions are met, the closing price is stored in myopen, and on is set to true to indicate an open position.
• Exit Condition: If there is an open position (on is true), and the Stochastic value crosses above 80 (overbought condition), the script records the closing price at this point into myclose. The difference between myclose and myopen (profit or loss) is calculated and stored in diff. The variable on is then reset to false to indicate that the position is closed.
• Output: The script returns the value of diff, which represents the profit or loss from the trade.

This snippet is a basic example of how to implement a trading strategy using the Stochastic Oscillator in the ProBuilder language, focusing on the logic to open and close trades based on specific indicator thresholds.