How to make my indicator update in real time?

Hello, fellow coders!

I have an indicator that shows me the price difference between the newest candles open and 21st candle close. This is working fine except for one crucial thing - it doent update with the chart. It keeps showing the value for when it was first added to the chart.

I have tried to add RefreshRates() and similiar functions but with no success so far. This is the code:

#property indicator_chart_window
//+------------------------------------------------------------------+
//| Custom indicator initialization function                         |
//+------------------------------------------------------------------+
int init()
  {
  double a=Open[0]-Close[20];
    string name;
    string par =DoubleToStr((a/Point),0);
   
       if(Open[0]>Close[20])
      {
       name = "  up = ";
      }
    if(Open[0]<Close[20])
      {
       name = "down = ";
      }
     if(Open[0]==Close[20])
      {
       name = "flat = ";
      }
 
   
 
 
   //
   ObjectCreate("signal",OBJ_LABEL,0,0,0,0,0);
   ObjectCreate("signal2",OBJ_LABEL,0,0,0,0,0);
 
   //
   ObjectSet("signal",OBJPROP_XDISTANCE,650);
   ObjectSet("signal2",OBJPROP_XDISTANCE,706);
 
   //
   ObjectSet("signal",OBJPROP_YDISTANCE,12);
   ObjectSet("signal2",OBJPROP_YDISTANCE,12);
 
   //
   ObjectSetText("signal",name,12,"Tahoma",Red);
   ObjectSetText("signal2",par,12,"Tahoma",Red);
  
 
   return(0); 
  }
//+------------------------------------------------------------------+
//| Custom indicator deinitialization function                       |
//+------------------------------------------------------------------+
int deinit()
  {
//----
//----
   return(0);
  }
//+------------------------------------------------------------------+
//| Custom indicator iteration function                              |
//+------------------------------------------------------------------+
int start()
  {
   int    counted_bars=IndicatorCounted();
//----
  
//----
   return(0);
  }

//+------------------------------------------------------------------+

What should be implemented into the code and where - in order for it to automatically update to each new candle open?

Every bit of help is highly appreciated!

Once again, I want to thank all who take their time - thinking about this problem of mine - in advance.

All have a nice day,

ruth26