how to take interfaces as parameters in ATL

hi,
I have a native c++ dll and two classes:

classA{
void setNumber(int number);
int getNumber();
}
classB{
void setclassA(classA);
classA getclassA();
}

I have an ATL dll that wraps the native C++ dll and two interfaces: InterfaceForClassA , InterfaceForClassB .

InterfaceForClassA :

STDMETHODIMP CInterfaceForClassA::createClassAObject(void)
{
         ClassA* Aobject = new ClassA();
         return S_OK;
}
STDMETHODIMP CInterfaceForClassA::setNumberInClassA(SHORT pVal)
{
          if(Aobject != NULL)
                Aobject->setNumber(pVal);
         return S_OK;
}

STDMETHODIMP CInterfaceForClassA::getNumberInClassA(SHORT* pVal)
{        
          if(Aobject != NULL)
              *pVal = Aobject->getNumber();
          return S_OK;
}
STDMETHODIMP CInterfaceForClassA::getClassA(VARIANT** pVal)
{
         *pVal = (VARIANT*)Aobject;
          return S_OK;
}
STDMETHODIMP CInterfaceForClassA::putClassA(VARIANT* newVal)
{
         Aobject = (ClassA*)newVal;
         return S_OK;
}

InterfaceForClassB :

STDMETHODIMP CInterfaceForClassB::setClassA(IInterfaceForClassA * val)
{

          ClassB* BObject = new ClassB();
          ClassA* objA = new ClassA();            
         val->getClassA((VARIANT**)&objA);
         BObject->putClassA(objA);
          return S_OK;
}

STDMETHODIMP CInterfaceForClassB::getClassA(IInterfaceForClassA ** returnVal)
{
          ClassA* objA = new ClassA();   
          IInterfaceForClassA *pY;
          objA = BObject->getClassA();        
          pY->putClassA((VARIANT*)&objA);
          *returnVal = pY;
          return S_OK;
}

and finally i have a c# project that includes that ATL dll, in the c# project i call ATL dll classes:

InterfaceForClassAClass classAInt = new InterfaceForClassAClass();
classAInt.createClassAObject();
classAInt.setNumberInClassA(5);
InterfaceForClassBClass classBInt = new InterfaceForClassBClass();
classBInt.setClassA(classAInt);
classBInt.getClassA();

it gives the 'System.ExecutionEngineException' at the line "classBInt.getClassA();" .
Can you help me please?

Tags: C++, ATL, DLL