Suzanne - great question. While there isn't currently an official way to lock your sign up (that feature is on our development list)... some people have found ways to do it. For example, I've seen people convert their sign up to a password-protected sign up right before the event and not tell anyone the password. That basically locks people out of the sign up and they can't change anything (or view anything). Keep in mind that the administrator does get email notifications any time someone updates their event and you can make the rules on what people can do. So... if you tell people they can't cancel within three days of the event... and someone does it anyways... you'll get notified by email and you can sign them right back up via the admin. Sadly, there's just no sure-fire way to stop people from bagging out on commitments. Even when we add our "lock" feature, there will be people just don't show up or send you an email saying they can't come! Frustrating for us organizers, I know! We feel your pain!
Katie... multiple administrators and notifications are features coming soon in our PRO version. For details on that, follow this link:
http://www.signupgenius.com/about/signupgenius-pro.cfm
Hope that helps!
