question about redirecting some ips to web page

[Dr.X]

hi ,

i want to ask about directing some ips to webpage .

my secenario is as below :

assume i have router R1  and i have 2  interfaces

interface Gi0/1  the users come from

interface Gi0/2  the users go to internet after AAA process and after successful authentication

here is simple graph

=======USERS===========Gi0/1--R--Gi0/2========>internet

during the authentication ,the users can have an ips .

i want the successful authentication to give them a puplic ips and they can reach the internet and go out interface Gi0/2

but in the same time , the users who have a fail authentication and who have toopay the bills , i want to  give them a special range of private  ips   and want each user if he opened his internet explorer to be directed to another special webpage internally .

can i  do what i wan ???

is it hard ??

im useing radius servers for AAA .

plz help

regards

[Dr.X]

my question is another forms :

if the router  recive an http packet with destination x.x.x.x    and the  src ip was from the private ips range ,

x.x.x.x   whatever the destination was ,

i want to router  to  direct the http traffic  to the destination y.y.y.y  , where y.y.y.y destination  is my local  web server .

regards