How to "Import from Matlab" into the "Group Analysis" folder

Hi all,

I am trying to recreate in script what I easily do by right-clicking on one of the folders within my Group Analysis on "Import From Matlab", with no success. I can easily do it for subjects, because I understand how to get the iStudy of each patient, but I can't understand how the group analysis is indexed. Any suggestions on how to do it?

The Group analysis subject can be retrieved like:
groupSub = bst_get('Subject', 'Group_analysis');

Then its studies are:
[sStudies, iStudies] = bst_get('StudyWithSubject', groupSub.FileName);

Thanks!!