Hello.

This task can´t be achieved by some native way, as opposite task. Without full source code, you can override RenderedHTML property of given breadcrumb control, and rip-off the page you do not want to be shown in navigation. This operation can be done in code-behind of given control (\CMSWebParts\Navigation\cmsbreadcrumbs.ascx.cs), so some customization is needed.

Best Regards,
Radek Macalik