Follow the same steps but instead of holding enter, try rapidly clicking the "Go" button. When the page changes rinse & repeat.
Alternatively, here's a greasemonkey script called "Auto Battler":
(you need an account to see links)
Have greasemonkey installed under FF, copy/paste that code into a new text file.
Just edit the variables "pet_name" to your pets' name (e.g.
var pet_name = *yourpet'snamehere*) and
var enemy_id = '20' to
var_enemy_id = '57'
Save the script as
108823.user.js and open it with Firefox. This will prompt you to install it.
Then just go to this page when logged in and run the script:
(you need an account to see links)