HOW TO CHANGE PUBLIC IP RANDOMLY EVERY TIME USER CONNECT.

my user get every time same public ip i want to do that my user should get new public ip every time he connect.. i am not using ippool file . my ips are stored in radgroupreply. my table content id,groupname,attribute,op,value 39 1024 Service-Type == Framed-User 40 1024 Mikrotik-Address-List = 1024 43 1024 Framed-Pool == all-ips 42 1024 Framed-Protocol == PPP thanks regards zubairayub