© 2010 Autodesk
Introduction to the Navisworks 2011 .NET API
Main Automation Class
static void Main(string[] args)
{
   NavisworksApplication app = new NavisworksApplication();
   app.OpenFile(@"C:\file\A.nwd");
   app.AppendFile(@"C:\file\B.nwd");
   app.ExecuteAddInPlugin(“Colouriser.ADSK");
   app.SaveFile(@"C:\files\Combined.nwd");
}
Autodesk.Navisworks.Api.Automation.NavisworksApplication
The automation interface is pretty sparse.
Most heavy lifting is expected to be done by a plugin.
Can also do everything here from the command line, but code might be required to do something a bit more sophisticated (e.g. Load all files from a directory).