Raise an issue, documentation issues are generally addressed pretty quickly. Although the team is in London at the moment. It’s also good to include the URL to the page you are talking about. You can get that by opening the documentation in a web browser and finding the page.
Are you using Listbox (deprecated) or DesktopListbox?
Is your Listbox in a container?
What event are you using?
What is the error/crash that you get?
Did you already file an Issue on the Xojo Issues Tracker?