How do I pass a com object to a callback function

Question

I am trying to program the PCI-6527 card within a COM object. With the DIG_Change_Message_Config command I'm setting the notification for when the input signal changes using a callback function. To make the callback function work I have to declare that function as a static member of the object class. This means that I have no access to the this pointer in this function. After I receive the notification, my actions in the callback function depend on settings in member variables in the class. MSDN gives as a solution to pass the this pointer as an argument to a static member function to have access to the class. I've tried this but the compiler keeps barfing at me.
The code used is:
stat = DIG_Change_Message_Config(
m_CardNum,1, msg,"",0,0, (unsigned long)DealWithInput );
with DealWithInput defined as: static void DealWithInput();
Is there a way of getting access to the class in DealWithInput either by passing it as an parameter or through some other ingenous trick that I can't find documentation for

Answer 1

The thing is that you cannot change the parameters of the callback functions. It is always :
void yourCallbackFunc (DAQEventHandle handle,
DAQEventMsg msg,
DAQEventWParam wParam,
DAQEventLParam lParam);
When yourCallbackFunc is called back, all the parameters get filled in the calling function in DAQ driver. What you have to do is pass the this pointer in message parameter in DIG_Change_Message_Config function, so that whatever you pass in message gets passed back in your callback function. Message can be any type.