MACD Histogram values

When using the MACD indicator on the chart it shows 2 values -  a Histogram and a Signal line.

If you use the iMACD() function to calculaute the MACD values you have 2 options - MODE_MAIN and MODE_SIGNAL.

I have always assumed thet MODE_MAIN represents the Histogram values.

Now to my dismay I discover that this is a fallacy! It represents the MACD values - of how it is calculated I have no idea! (But I can find out if I am interested)

My trading decisions are based on the MACD Histogram values (among others) and now I find out that if I use MODE_MAIN I get incorrect values.

It seems there is a way to use iCustom() with "iMACD" as the indicator name to get these values - or I have to write code to calculate these values.

Which is the best way? or can it be done with iMACD also?

If code is required is the following code correct?

//Define Inputs
input int  period  = 100;

// define the MACD parameters
int fast_ema_period = 12;
int slow_ema_period = 26;
int signal_period = 9;

// calculate the MACD values
double macd_main[], macd_signal[];
int macd_handle = iMACD(_Symbol, _Period, fast_ema_period, slow_ema_period, signal_period, PRICE_CLOSE);
CopyBuffer(macd_handle, 0, 0, period, macd_main);
CopyBuffer(macd_handle, 1, 0, period, macd_signal);
IndicatorRelease(macd_handle);

// calculate the MACD histogram values
double macd_histogram[];
for(int i = 0; i < period; i++)
{
    macd_histogram[i] = macd_main[i] - macd_signal[i];
}

// output the MACD histogram values to the Experts tab
for(int i = 0; i < period; i++)
{
    Print("MACD Histogram[", i, "]: ", macd_histogram[i]);
}