HELP!!!! False MACD Crossover

I'm calculating MACD and the histogram values as such and putting an arrow on the chart. Periodically I will get a false crossover signal. Can anyone tell me why and help me fix it?

Thanks very much in advance,

E

MacdCurrent=iMACD(NULL,0,8,17,9,PRICE_CLOSE,MODE_MAIN,0);
MacdPrevious=iMACD(NULL,0,8,17,9,PRICE_CLOSE,MODE_MAIN,1);

SignalCurrent=iMACD(NULL,0,8,17,9,PRICE_CLOSE,MODE_SIGNAL,0);
SignalPrevious=iMACD(NULL,0,8,17,9,PRICE_CLOSE,MODE_SIGNAL,1);

MacdHist = MacdCurrent - SignalCurrent;

if(MacdHist > 0 && MacdCurrent > SignalCurrent && MacdPrevious < SignalPrevious)
-- Draw Arrow

if(MacdHist < 0 && MacdCurrent < SignalCurrent && MacdPrevious > SignalPrevious)
-- Draw Arrow

First thing that comes to mind is that you're checking for the crossover on the current bar. This means you can get a cross, then price retracts and the cross goes away. You've already drawn the arrow, so there it stays.

This is how it's being done all over the place, is everyone doing it wrong? Here is the example that I got from MQL4.com.

http://articles.mql4.com/84

How do I fix it?

Thanks,

Ed