调用com+对象的一个问题

得到接口指针就使用其中的方法
HRESULT hr;
IRmtObject *pRmtObject;
LPUNKNOWN pUnknown;
hr=CoCreateInstanceEx(CLSID_RmtObject ,NULL,CLSCTX_SERVER,&ServerInfo,2,(MULTI_QI*)&qi);
//hr=::CoCreateInstance(clsid,NULL,CLSCTX_SERVER,IID_IUnknown,(LPVOID FAR *)&pUnknown);
   if(FAILED(hr))
   {
         goto end;
    }
int z;
pUnknown=qi[0].pItf;
hr=pUnknown->QueryInterface(IID_IRmtObject,(void **)&pRmtObject);
pRmtObject->Sum(x,y,&z);
         pUnknown->Release();
pRmtObject->Release();