LotsRisk - library for MetaTrader 4

Parameters:

• riskPercent - percent of the current balance you want to risk
  
• sl - the value of the StopLoss for the given order
  
• price - the open price of the order
• error - refereced parameter. an error code, that is returned by the function
  

Note: I can't say that it works correctly. I've checked it approximately. So your comments are appreciated.

Here is an example:

   int riskPercentage = 3,
      error;
   double sl = Ask - 40 * Point,
      openPrice = Ask;   

   double lots = GetNeccessaryLotsWithRisk(riskPercentage, sl, openPrice, error);
   
   if (CompareDoubles(lots, 0))
   {
      switch (error)
      {
         case LOTS_TOO_BIG:   // lots are bigger than max lots
            Alert("Risk percentage is too big");
            break;

         case LOTS_TOO_SMALL: // lots are smaller than min lots
            Alert("Risk percentage is too small");
            break;

         default:             // formula's result =)
            Alert("It seems like you've got $0 or stoploss is too far");
            break;
      }
   }