client to see "/" on log-in

[<shyamk@eth.net>]

I want my ftp clients who log-in to my server to see
their home directory as "/" and not to be able to "cd  .."

eg : a client xyz.com , whom I have given a user account xyz
 ftp-s into my server (running proftpd) , does a pwd from her machine ,
sees the  output as "/home/www/site/xyz"
does "cd .."  or  " ls .. "  , and  gets to see things ( at least -
directories ) , which information  I do not want her to see . She should
get the feeling that she is sitting at the top , a pwd should give "/"
as output , and no "cd .." or "ls .." should not be possible for her.

How do I accomplish this ?

Thanks,
Shyam