Craig,
The internet toolkit functions are on a separate instrument that you need to load in order to have CVI include the .h files requiered automatiacally and to have access to the functions in the menu.
To load the instrument go to "Instrument>>load..." you should be able to find it in the CVI installation directory (C:\Program Files\National Instruments\CVI\....). It is also a good idea to include that fp int he project so that you don't have to loaded it again.
Hope that helps, let me know if you have any questions.
Regards,
Juan Carlos
N.I.