More Information about:
Link: 1) en.wikipedia.org/wiki/Price_and_Volume_Trend
Link: 2) www.incrediblecharts.com/indicators/price_and_volume_trend.php
Link: 3) http://ta.mql4.com/indicators/volumes/price_trend



Calculation:

We get PVT by multiplying the current volume by the relative change of the share price and adding the result to the current cumulate value of the indicator.

PVT (i) = ((CLOSE (i) - CLOSE (i - 1)) / CLOSE (i - 1)) * VOLUME (i) + PVT (i - 1)

Where:

CLOSE (i) — the closing price of the current bar;
CLOSE (i - n) — the closing price n bars ago;
VOLUME (i) — the volume of the current bar;
PVT (i) — the current value of PVT indicator;
PVT (i - 1) — the value of PVT indicator on the previous bar.

Source Code "Price Volume Trend":

function init()
{
   with (PVT) {
     label = "PVT";
     createBuffer("PVT");
     setBufferColor("PVT", "lime");
     setBufferDrawStyle("PVT", DrawStyle.LINE);
     setAutoChangeMaxMin("PVT");
   }
}

function start()
{
   var num = Shared.numberOfQuotes();
   var PVTbuf = new Array(num);

   PVTbuf[0] = 0;
   for (var j = 1; j < num; ++j) {
     PVTbuf[j] = (((Shared.close(j) - Shared.close(j-1))/Shared.close(j-1)) * Shared.volume(j) + PVTbuf[j-1]);
   }

   PVT.setBufferData("PVT", PVTbuf);
}