1. Firstly reset your profit at the beginning of each weeek (the first bar whose OpenDayOfWeek = 1) and re-enable trading
2. Secondly monitor when STRATEGYPROFIT exceeds your weekly Gains and, if so, disable further trading using a variable named TRADEON

There you go:

ONCE MyProfit = 0               //Use this variable to tell when your profit exceeds X
ONCE TradeON  = 1               //1=trading enabled, 0=trading disabled
ONCE X        = 500             //500 € max weekly profit
IF OpenDayOfWeek = 1 AND OpenDayOfWeek[1] <> 1 THEN   //at week start
   MyProfit   = StrategyProfit  //save the total profit at the start of the week
   TradeON    = 1               //re-enable trading
ENDIF
IF (StrategyProfit - MyProfit) >= X THEN
   TradeON    = 0               //disable trading after X € gained
ENDIF
IF MyLongConditions AND Not OnMarket ANd TradeON THEN //add TradeON as an additional condition to enter a tarde
   BUY 1 Contract AT Market
ENDIF

At line 3 use a percentage (1, 2, 3.5, etc…) instead of money.

Replace line 8 with:

IF (StrategyProfit - MyProfit) >= abs(MyProfit * X / 100) THEN