Generate buy and sell signals

Algos, strategies, code
1

Need to code in pi when:
when macd histogram goes above or low from the zero line? Thank you.

2

For the above given condition
Buy Script:

SET A = MACDSignal(13, 26, 9, SIMPLE)
SET B = MACD(13, 26, 9, SIMPLE)
CROSSOVER(A, B) = TRUE

Sell Script:

SET A = MACDSignal(13, 26, 9, SIMPLE)
SET B = MACD(13, 26, 9, SIMPLE)
CROSSOVER(B, A) = TRUE