Hello!
Declare a VARIANT (as follows) and use that variable in the place of the optional parameters that you don't want to use:
COleVariant vOptional((long)DISP_E_PARAMNOTFOUND, VT_ERROR);
Both Visual Basic and Visual C++ allow the use of optional parameters when calling functions; however, the Visual C++ wizard that writes your C++ wrapper around the ActiveX control when it is added to the project is usually not smart enough to incorporate this functionality (since it has no idea what parameters may or may not be necessary). The way to achieve this effect is to pass a VARIANT with a special setting that the control will interpret as "not used."
In the code above, I create the variable vOptional set to this special code; I can use this variable whenever I don't want
to pass something as an optional parameter. Be sure to check the documentation for your ActiveX control to make sure that the parameter is indeed optional. For ComponentWorks controls, optional parameters are shown in brackets ([]) in the ComponentWorks Help File.
Regards,
Chris Wood
Applications Engineer
National Instruments
