A while ago, Dooglus posted a script he made:

https://bitcointalk.org/index.php?topic=709185.msg9379308#msg9379308which seems like it would fit your purposes. Since then there's been a minor API change, so here's the adapted version:

var baseBet = 10; // in Bits

var cashout;

var mult;

// set one of mult or cashout, and the other will be calculated for you:

// mult = 1.12;

cashout = 1.5;

// what percentage to increase the net profit by each time we lose a bet; 0 for pure martingale

greed_percent = 5;

if (!mult)

mult = cashout / (cashout - 1) * (1 + greed_percent/100);

else if (!cashout)

cashout = mult / (mult - 1) * (1 + greed_percent/100);

var satoshis = baseBet * 100;

var crash = Math.floor(cashout*100 + 1e-6);

var currentBet = false;

engine.on('game_starting', function () {

if (currentBet && engine.lastGamePlay() === 'LOST')

currentBet *= mult;

else

currentBet = satoshis;

if (currentBet < engine.getBalance()) {

console.log('place bet of', Math.round(currentBet/100), 'at', crash/100);

engine.placeBet(Math.round(currentBet/100)*100, crash, false);

}

else {

engine.stop();

console.log('You ran out of bits :(');

}

});

Give that a go, and let me know if it fits your needs