Here's another Michael Gibson post on a similar matter:

8785.2 In reply to 8785.1
Hi eric, there's a CloseCurve command for MoI here: http://moi3d.com/forum/index.php?webtag=MOI&msg=2752.2 . That will make a line segment between the ends of an open curve like the Rhino CloseCrv command.

Hope that's what you were looking for!

- Michael

Cheers,
Mindset