This ProBuilder script demonstrates how to dynamically adjust the size of a trading position based on the profitability of the previous trade. The code snippet below shows how to increase the lot size by a percentage if the last trade was profitable.

ONCE LotSize = 1
ONCE PerCent = 1.2
ONCE TP = 30
ONCE SL = 100

IF StrategyProfit > StrategyProfit[1] THEN
    LotSize = LotSize * PerCent
ENDIF

// Conditions to enter long positions
c1 = (RSIind < 30) //RSI upward momentum

// Conditions to enter long positions
IF NOT LongOnMarket AND c1 THEN
    BUY LotSize CONTRACTS AT MARKET
    Set target pprofit TP
    SET STOP pLOSS SL
ENDIF

Explanation of the Code:

• Initialization: The variables LotSize, PerCent, TP (Take Profit), and SL (Stop Loss) are initialized using the ONCE keyword, which ensures they are set only once and retain their values throughout the execution of the script.
• Profit Check: The script checks if the current strategy profit (StrategyProfit) is greater than the strategy profit of the previous bar (StrategyProfit[1]). If true, it multiplies the LotSize by PerCent (1.2 in this case), effectively increasing the position size by 20%.
• Trading Condition: The condition to enter a long position is defined by c1, which checks if the RSI indicator value is below 30, suggesting potential upward momentum.
• Trade Execution: If there is no existing long position (NOT LongOnMarket) and condition c1 is true, the script executes a buy order with the adjusted LotSize. It also sets the take profit and stop loss levels as specified by TP and SL.

This snippet is a practical example of how to implement a dynamic position sizing strategy based on the performance of previous trades, using basic trading indicators and profit tracking in ProBuilder.