Multithreaded callback.

1. Encapsulate the Fire_... function into an interface method.

   Add the method Fire_actionMethod() to the interface main and provide the implementation:

   STDMETHODIMP CTheCoClass::Fire_actionMethod()
   {
   	Fire_action();
   	return S_OK;
   }
   

2. Open callBackServer project and change the mainMethod...

   as follows:

   
   DWORD WINAPI timerThreadProcedure( void* p )
   {
   	CoInitialize(NULL);
   	IMain* i=(IMain *)p;
   	for( int j=1; j<=10; ++j )
   	{
   		Sleep(1000);
   		i->Fire_actionMethod();
   	}
   	i->Release();
   	CoUninitialize();
   	return 0;
   }
   
   STDMETHODIMP CTheCoClass::mainMethod()
   {
   	IMain* ptr;
   	QueryInterface(IID_IMain,(void**)&ptr);
   	CreateThread(NULL,0,timerThreadProcedure,ptr,0,0);
   	return S_OK;
   }
   
   




3. Test client.

   		
   Dim WithEvents server As CALLBACKSERVERLib.TheCoClass
   Dim i As Integer
   
   Private Sub server_action()
       i = i + 1
   End Sub
   
   Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
       If server Is Nothing Then
           Set server = New CALLBACKSERVERLib.TheCoClass
       End If
       server.mainMethod
   End Sub
   
   Private Sub Worksheet_BeforeRightClick(ByVal Target As Range, Cancel As Boolean)
       ActiveCell.Value = i
   End Sub
   
   

4. Important note

   You cannot modify cells directly in the callback function.
   If user opens a modal dialog box then the messages will be lost. One really have to store them in some intermediate layer and ask the layer repeatedly.