Thank's for your quick answers.
Rapid Dr3am: I will use delimited text.
Graham: I saw you mod but i need to add an option that add all the import list in to a group. But i don't know if i need to consisting the personal group of the user or user id. Is the personal group of a user is use to connect him to other group like that?
User <-- Personal Group <--- Global Group ?
User <-- Personal Group
User <-- Global Group
The real Q is for what we use "Personal Group"?
I already did it. 1 hour writing, not big problem. 8)