ok guys....i hav foun it...bt it is a bit bad for this UI...n its nt upto the mark..
ok here is how to do it
got to groups> select group name> add members> it's upto u to add how much ever u want> now take the specific contact added in the group > options > go down u can see assign ringtone> select the ringtone>>
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hope this was helpul
Thanks....:applause: