bastion=xyz.com
user=$( whoami )

function doSSH () {

    ssh $user@$bastion -t -A
        -L 5900:127.0.0.1:5900
            ssh $user@$1 -t -A
                -L 5900:127.0.0.1:5900
                /opt/enableVNC
}

$ doSSH node1
user@bastion's password:
user@node1's password:
hi
Connection to node1 closed.
<hang>