Want formmail to be previewed (not validated) before submit

I am now working with an HTML version of a contact form using Custom Contact Forms plugin, and while it works fine, I’m hoping to either tweak it or find a plugin that will allow a user to preview their information before sending it via formmail. Just about every other plugin I have seen just sends the email without giving any preview (not validation).

Any suggestions? This one’s driving me up the wall. Thanks!