How to make email sending conditional?

I have a contact form with a "send a copy to yourself" checkbox and an optional email field. How do I make the email action run only if the person has checked "Send me a copy"? I'm sure there's an easy way but I just can't figure it out.

Thanks in advance for your help.

Never mind. Turns out Greyhead has written a free action for this:

http://greyhead.net/how-to-docs/cfv4-email-gh-action