how to change public ip for customers ??!!

Hello
how to change static public ip my customers for sites megaulpoad.com, rapidshare.de etc. using scripts ?
im use pppoe-server

My cfg:
interface ether1 xxx.xxx.xxx.x01/24
interface ether1 xxx.xxx.xxx.x02/32
interface ether1 xxx.xxx.xxx.x03/24
interface ether1 xxx.xxx.xxx.x04/24
interface ether1 xxx.xxx.xxx.x05/24
interface ether1 xxx.xxx.xxx.x06/24
itd..

interface bridge1 is wlan1,wlan2,wlan3

ip firewall /
chain=srcnat action=masquerade out-interface=bridge1
chain=dstnat action=dst-nat to-addresses=10.100.8.02 to-ports=0-65535 dst-address=xxx.xxx.xxx.x02
chain=dstnat action=dst-nat to-addresses=10.100.8.03 to-ports=0-65535 dst-address=xxx.xxx.xxx.x03
itd…

interface pppoe-server/server
service-name=“service1” interface=bridge2 max-mtu=1440 max-mru=1440 authentication=pap,chap,mschap1,mschap2 keepalive-timeout=15 one-session-per-host=yes max-sessions=0 default-profile=default

/ppp secret
name=“abc” password=“abc” service=“pppoe” profile=“default” remote-address=10.100.8.02
name=“abc1” password=“abc1” service=“pppoe” profile=“default” remote-address=10.100.8.03

this cfg is work fine, plis help me how to change static public ip to dynamic

IP → DHCP-Client