Blocking spiders from website

Hi
I have a guestbook on a friend's site...I am currently hosting the site for him but we are going to re design the site...
anyhow - we are currently getting about 200 guestbook entries a day from this address (according to my web stats) http://umax-se.com/like.cgi?query=http://www.jamierees.co.uk/ps2/ps2games/guestbook/ardguest.php?do=add (btw if you click on it, it adds more S**t to the old guestbook)

It keeps adding random entries to this guestbook....now in the past I've used

order allow,deny
deny from persons.ip.address
allow from all

in the past but I don't know if this will work for banning specific target URL's..

any one have any ideas whether this will work or not?

i's not realy a spider ...

the easiest sollution is to change your guestbookcode and include a dynalically generated securityimage they need to type over before submitting a comment.

Ye..I might do that - however I'm going to take that guestbook down I think as that site kinda died..