SendMessage from javascript to c

Hello,

I need to send a message from javascript back to my c# code, but i keep getting error.

in c# i have

public class OpenClass : MonoBehaviour {

public void GetMessage(string msg)
{
Debug.Log("message="+msg);
}
}

in java script I have
SendMessage('OpenClass','GetMessage','hello');

I keep getting error in FireFox console like this:
sendMessage: object OpenClass not found:


What should be the first parameter for the sendMessage function in my case?
Do I need to make OpenClass static? or GetMessage static? I dont understand what it wants!

I read that the first parameter is the gameObject, but there are no gameobjects in Javascript, so i dont understand what to put for that. Is that the name of the object in the hierarchy window that contains this class?

Thanks for any help