StopLevel = 1 - Param("trailing stop %", 3, 0.1, 10, 0.1)/100;

Buy = Cross( MACD(), Signal() );
Sell = 0;
trailARRAY = Null;
trailstop = 0;

for( i = 1; i < BarCount; i++ )
{

   if( trailstop == 0 AND Buy[ i ] ) 
   { 
      trailstop = High[ i ] * stoplevel;
   }
   else Buy[ i ] = 0; // remove excess buy signals

   if( trailstop > 0 AND Low[ i ] < trailstop )
   {
      Sell[ i ] = 1;
      SellPrice[ i ] = trailstop;
      trailstop = 0;
   }

   if( trailstop > 0 )
   {   
      trailstop = Max( High[ i ] * stoplevel, trailstop );
      trailARRAY[ i ] = trailstop;
   }

}

PlotShapes(Buy*shapeUpArrow,colorGreen,0,Low);
PlotShapes(Sell*shapeDownArrow,colorRed,0,High);

Plot( Close,"Price",colorBlack,styleBar);
Plot( trailARRAY,"trailing stop level", colorRed );