[Plugin: Contact Form 7] Preventing Multiple Form Submissions

Hi,

Has anyone ever tried to implement any sort of form validation based on previous submissions (the click of the submit button)? I’m using wpcf7 for a survey that I’m conducting and I’d like to find a way to prevent people from submitting the form multiple times. It doesn’t have to be anything crazy intense like preventing submissions based on IP address (which I’m sure is impossible since the data isn’t being collected in a database), but something to prevent the casual user from easily submitting multiple surveys. I know there are multiple hooks that contact form uses, but I don’t really know where to start with that. Any ideas would be greatly appreciated!