forwarding multi pppoe client to multi pppoe accounts

hi all,

i have the following situation:
i have 20 pppoe accounts from my isp
and i have 30 users which have never be online together(max 15 online)
i need to make my router board connect all the pppoe accounts from ether1
and every client when connected to ether2 (on which i ve created a pppoe server) he will be forwarded to any of the 20 pppoe account connected to the isp server through ether1.

i know that this is possible for every user to be forwarded to specific account coz one of my friend have done it b4 but i m not being able to contact him for now.
as for the dynamic forwarding to any of the account i don’t know if this is possible

and thanks for anyone who can help