Providing that the group names are there, and you say that they are, then probably the easiest way is to write a hierarchy file and bring it in that way. Details are in the manual but you may find this page easier.

http://www.philc.net/HierarchyBuilder.php

Please note that you do not have to use my utility, you can write a PHI file in Notepad and other editors are out there. My main reason in posting is to say that this is the method that I would use and to point you to what is basically a tutorial on how to write hierarchy files.

Hope that helps.