string CheckEntry()
 { 
 
      // string for the signal
      string signal =""; 
      
      // define the IAC
      float IADValue=iAD(_Symbol,_Period,0);      
      
      // if it is above 0
      if (IADValue>0)
      signal="sell"; 
      
      // if it is below 0   
      if (IADValue<0)
      signal="buy";
      
      // return the signal to the main module
      return signal;                        
     
 }