Hi Simon,
There is a function that can be called from CVI that will display a .chm file. The function is ShowHtmlHelp();. By specifying the .chm file you want to use, CVI will launch that file in a standard help window.
To use this with a help menu, you can simply create a callback for your help button or menu and then put ShowHtmlHelp() into the callback. Include the .chm file with any distributions and you should be sorted!
Hope this helps,
Tom
Applications Engineering, NI UK