[babel] passing strings in

[Maurizio Vitale <mav@cuma.i-did-not-set--mail-host-address--so-tickle-me>]

In the table/block pair below, I'm trying to pass an IP number to some
shell code. It seems like in the table formula I can only have
numbers. Is that right?

#+TBLNAME: system-host-ping :var host=system-hosts
| name      |             ip | ping   |
|-----------+----------------+--------|
| host 1    | 192.168.10.200 | #ERROR |
| host 2    |  192.168.10.24 | #ERROR |
| host 3    |  192.168.42.24 | #ERROR |
#+TBLFM: $3='(sbe system-ping (ip $2))'

#+source: system-ping
#+begin_src sh 
# This is what I eventually want
#ping -w 10 -c 1 -q $ip >/dev/null 2>&1
#echo $?

# Testing
echo $ip
#+end_src

Any way to pass arbitrary strings?

Thanks a lot,

       Maurizio