ObectCreate() function sub window parameter?

[Stephen Reynolds]

In the code below I'm trying to draw a simple object on a sub window :

// Input variables 
input int KPeriod = 14;
input int DPeriod = 3;
input int Slowing = 3;
input ENUM_MA_METHOD StochMethod = MODE_SMA;
input ENUM_STO_PRICE StochPrice = STO_LOWHIGH;

// OnTick() event handler                
void OnInit() 
{  
   double stoch=iStochastic(_Symbol,_Period,KPeriod,DPeriod,Slowing,StochMethod,StochPrice,MODE_MAIN,0);
   datetime time=iTime(NULL,0,0);

   bool line1=ObjectCreate("Thumb",OBJ_ARROW_THUMB_UP,0,time,stoch);
}

Why cant I get the ObjectCreate() function to put an object on sub window? I've put 1 on 3rd parameter as required but it still doesn't draw any object?
When I place 0 it does draw the object okay on the main chart but why not stochastic?

Here I'm confused? I'm beginning to think ObjectCreate () can only draw objects on main window?