Override path to binary for particular user

If the binary is in /usr/bin/binary and the script invokes the binary without specifying the full path, but instead relies on /usr/bin being in PATH then you can simply add the location of the new binary to the beginning of the user's PATH. Put something like this in their ~/.bashrc:

PATH=/mount/new_version:$PATH

For security reasons, scripts often specify the full path to binaries to prevent this kind of thing.

If you have access to the binary you can backup it and create a symbolic link.

mv /urs/bin/binary /urs/bin/binary.bkp
ln -s /mount/new_version/binary /urs/bin/binary

[EDIT]

Sorry, didn't saw the change must be done for one user only.

You can create a function to be called instead of the binary.

Depending on how you execute the binary (full path or just name) you must create a suitable function, like:

# Full path
function /urs/bin/binary () { command /mount/new_version/binary "$@"; }
export -f /urs/bin/binary
# Name
function binary () { command /mount/new_version/binary "$@"; }
export -f binary

If the binary don't accept/need arguments, remove the "$@".

To automatize the function creation, put the function lines in the .profile file in the user home directory.

alias commandname=/mount/new_version/binary

in the .bashrc above the path statement/export or in the profile will accomplish easy enough.