This ProBuilder script is designed to track the outcomes of the last three trades and change a flag based on a specific sequence of wins and losses. The code also includes conditions for entering trades based on a moving average crossover strategy, and visualizes the trade outcomes and the flag status on the chart.

ONCE MyProfit1 = 0
ONCE MyProfit2 = 0
ONCE MyProfit3 = 0
ONCE LWL = 0
IF LWL THEN MyProfit1 = 0 ENDIF
If StrategyProfit > StrategyProfit[1] then
    MyProfit1 = MyProfit2
    MyProfit2 = MyProfit3
    MyProfit3 = 1
ElsIf StrategyProfit < StrategyProfit[1] then
    MyProfit1 = MyProfit2
    MyProfit2 = MyProfit3
    MyProfit3 = -1
Endif
LWL = (MyProfit1 = -1) AND (MyProfit2 = 1) AND (MyProfit3 = -1)
IF close crosses over average[20] and Not LongOnMarket then
    buy at market
elsif close crosses under average[20] and Not ShortOnMarket then
    sellshort at market
endif
set stop ploss 100
set target pprofit 300
graph LWL coloured(255,0,0,255)
graph MyProfit1
graph MyProfit2
graph MyProfit3

Explanation of the Code:

• Initialization: The variables MyProfit1, MyProfit2, MyProfit3, and LWL are initialized to zero using the ONCE keyword, ensuring they are set only once when the script starts.
• Tracking Trade Outcomes: The script checks if the current strategy profit is greater or less than the previous period's strategy profit to determine if the trade was a win (1) or a loss (-1). These values are then shifted between MyProfit1, MyProfit2, and MyProfit3 to keep a record of the last three trades.
• Setting the LWL Flag: The LWL flag is set to true (1) if the sequence of last three trades is Loss-Win-Loss (MyProfit1 = -1, MyProfit2 = 1, MyProfit3 = -1).
• Trade Execution: The script executes a buy order if the close price crosses over a 20-period moving average and there is no existing long position, and a sell short order if the close price crosses under the moving average without an existing short position.
• Trade Management: A stop loss and a profit target are set at 100 and 300 points, respectively.
• Visualization: The LWL flag and the values of MyProfit1, MyProfit2, and MyProfit3 are graphed on the chart, with the LWL flag highlighted in red when true.