objects talking to each other

[Incrue]

I want objA to fire some function in objB
The name of object to fire and the name of the function must be inside variables in objA
The problem is:in AS2 this works, but in AS3,it dont:

code:

---

var objA = new Object();

var objB = new Object();



objB.doThis = function(){

trace("objB doing this");

}



objA.obName = "objB";

objA.funcName = "doThis";

objA[obName][funcName]();

---

So, what i do?
Thanks in advance