thanks Yil.
I'm managing a leech site used by my friends, so there's only the differents in speedlimit but credits.
so the function i required is really needed for me.
the "gadduser" command is excuted automatically by linux machine, so flashfxp cant be helpful.
Hope we could use the io with this function just like glftpd as u said,
there are files in /users called "default.GROUP1", "default.GROUP2".... then it could be loaded when gadduser GROUP1 ....