Q: Why are you using backslashes?
What you want to do is rather difficult if the user can log in as ordinary user, but we can guess that user will not need any commands unix specific am I right? As to do in simple way what you want, it would be to configure the user like an ftp user with a valid login shell false ( has to be valid: exist in /etc/shells ) perhaps and so access only using some ftp standards and the directory you want him to access only should be his home directory
Just quick thoughts...