You would like to limit your registration to a certain group of people. This may be because only your organization members can register or you are offering a complimentary registration to invited guests.
You can accomplish this through the Registration Login Required function available at Events -> Settings -> Advanced Settings. Set the Registration Login Required to Yes. Then enter a password in the Registration Login Password field.
Email your event prospects with the password information. Only upon successfully entering the password will users see your registration page. Using this feature, you will not allow those outside of your constituent group to view your registration page or costs.