Thanks for your help.

I think you did not understand what i wanted to do, but don't worry, i'll do it another way.

I will process all the groups (and all the users) to get their members, and in a second step process these data to obtain the result.

After seeking many docs, i think it's not possible to do what i wanted : not get the members of a group but get the "memberOf" of a group.
The kix test function InGroup works with all groups (including undirect groups) for the current user because i think it uses the IsMember test method of the ADSgroup object. There is no method to retreive the whole "memberOf" list for groups.

Again thanks.