This ProBuilder code snippet demonstrates how to implement a trailing stop loss strategy that adjusts based on the high or low prices from three bars ago. The strategy is designed for both long and short positions in trading.

Not tested:
IF MyLongConditions AND Not OnMarket THEN
    BUY 1 CONTRACT AT MARKET
    NewSL = low[3]-1*pipsize
    SELL AT NewSL STOP
ENDIF

IF MyShortConditions AND Not OnMarket THEN
    SELLSHORT 1 CONTRACT AT MARKET
    NewSL = high[3]+1*pipsize
    EXITSHORT AT NewSL STOP
ENDIF

IF OnMarket THEN
    IF PositionPerf > 0 THEN
        IF LongOnMarket THEN
            NewSL = max(newSL,low[3]-1*pipsize)
        ELSE
            NewSL = min(newSL,high[3]+1*pipsize)
        ENDIF
    ENDIF
    IF NewSL > 0 THEN
        SELL AT NewSL STOP
        EXITSHORT AT NewSL STOP
    ENDIF
ENDIF

Explanation of the Code:

• The code starts by checking if the conditions for entering a long position (MyLongConditions) are met and if there is currently no open market position (Not OnMarket). If both conditions are true, it executes a buy order for one contract at the market price. It then sets a new stop loss (NewSL) at the low price of the bar three bars ago minus one pip.
• Similarly, for a short position, the code checks if the conditions for entering a short position (MyShortConditions) are met and if there is no open market position. If true, it executes a sell short order for one contract at the market price and sets the stop loss at the high of the bar three bars ago plus one pip.
• If there is an open market position (OnMarket), the code then checks if the current position is profitable (PositionPerf > 0). If profitable and it’s a long position, it updates the stop loss to be the maximum of the current stop loss or the low of the bar three bars ago minus one pip. For a short position, it updates the stop loss to be the minimum of the current stop loss or the high of the bar three bars ago plus one pip.
• If the new stop loss (NewSL) is greater than zero, the code places a stop order to sell (for long positions) or to exit short (for short positions) at the new stop loss level.

This code snippet is useful for traders looking to protect their profits by adjusting their stop loss levels based on recent market movements, specifically targeting the highs and lows from three bars prior.