classes as out parameters

I have some classes defined in Slice like this: (Once again, I apologize for any syntax errors or typos)

class Command {...};

class Response {...};

class CommandSpec extends Command {...};

class ResponseSpec extends Response {...};

class MyModule {
    ...
    void sendCommand(Command cmd, out Response resp);
};

In my C++ code, I derive the above classes and attempt the following:

...
Ice::ObjectPrx base = mpIce->stringToProxy(...);
MyModulePrx mod = MyModulePrx::checkedCast(base);
...

mod->sendCommand(new CommandSpec(...), new ResponseSpec(...));

and I get something like the following error:
Error 2 error C2664: 'void IceProxy::MyModule::sendCommand(const CommandPtr &,ResponsePtr &)' : cannot convert parameter 2 from ResponseSpec *' to 'Response &'...

I can get around the problem by creating a ResponsePtr like this:

ResponseSpec r = new ResponseSpec(...);
ResponsePtr resp(r);

and calling sendCommand:

mod->sendCommand(new CommandSpec(...), resp);

OR...If I change the Slice signature of sendCommand command to:

void sendCommand(Command cmd, Response resp);

and change my C++ code specializations to reflect this change (by removing "const" from the resp parameter) then everything compiles.

I would like to simply pass in specializations of Response (such as ResponseSpec) without needing to first create a Ptr instance.

Is this doable? I know its probably something silly that I am not grasping here, but I just cant seem to figure this out.

Thanks,
Nick