No, because what's displayed in the form is browser-dependant. One thing you can do is have the script send small page with a meta-redirect to the "Thank You" page on success. That sort of prevents people from clicking "Back" to get to the form. It's imperfect.

Another technique to consider is to have a hidden "id" field in your form. The "id" would be unique (generated from a counter, say) so if someone tried to submit the same form twice, they'd get an error. This is also imperfect, as it can be spoofed (i.e. someone can manually change the "id" field), but perhaps for your application that's all right.