Basically CVI custom controls are built upon existing controls with or wirhout a librar that handles them. I mean: the "Quit button" custom control is just a standard command button with predefined labels and callback but with no associated code. This control adds very little value to the application and can be recreated from scratch or you can use the UI to Code Converter utility to make the job for you.
In case a more complex customization is present, there is normally a Instrument Driver (.fp and associated .lib or so) that should offer functiions to programmatically create and operate on the control. Just as an example, the File Browser custom control is built on top of a graph control; the associated library offers a FileBrowser_Create () function whose help recitates "Creates a new file browser from an existing tree control."
