//+------------------------------------------------------------------+
//|                                                         VROC.mq4 |
//|                      Copyright © 2007, MetaQuotes Software Corp. |
//|                                        http://www.metaquotes.ru/ |
//+------------------------------------------------------------------+
#property copyright "Copyright © 2007, MetaQuotes Software Corp."
#property link      "http://www.metaquotes.ru/"
//----
#property indicator_separate_window
#property indicator_buffers 1
#property indicator_color1 Green
//---- input parameters
extern int PeriodROC = 25;
//---- buffers
double ExtMapBuffer1[];
//+------------------------------------------------------------------+
//| Custom indicator initialization function                         |
//+------------------------------------------------------------------+
int init()
  {
//---- indicators
   SetIndexStyle(0, DRAW_LINE);
   SetIndexBuffer(0, ExtMapBuffer1);
   IndicatorShortName("VROC(" + PeriodROC + ")");
   IndicatorDigits(2);
//----
   return(0);
  }
//+------------------------------------------------------------------+
//| Custom indicator deinitialization function                       |
//+------------------------------------------------------------------+
int deinit()
  {
//----
   return(0);
  }
//+------------------------------------------------------------------+
//| Custom indicator iteration function                              |
//+------------------------------------------------------------------+
int start()
  {
   int counted_bars = IndicatorCounted();
   int i, limit;
//----
   if(counted_bars == 0) 
       limit = Bars - PeriodROC;
   if(counted_bars > 0) 
       limit = Bars - counted_bars;
   limit--;
   for(i = limit; i >= 0; i--)
       ExtMapBuffer1[i] = (Volume[i] - Volume[i + PeriodROC]) / 
                          Volume[i+PeriodROC]*100;
//----
   return(0);
  }
//+------------------------------------------------------------------+