Why don't you register the DLL and use ActiveX Automation in LabVIEW to communicate with Automation Server instead of passing IDispatch. I don't think labview would directly accept the IDispatch. The only possible way might be to write a wrapper DLL for that. I have created ActiveX DLL in VB, and called the method and properties on it without any problem from LV. The only thing you might wana keep in mind, is to register DLL and launch LV afterwards.