You can restrict ticket levels with access codes. A registrant will need to enter your code in order to be able to select the level. The access code does not change the amount or discount the ticket, it just restricts access to being able to select the ticket for purchase. On the event page, Event Setup tab, Levels sub-tab, you can add or edit an access code. Toggle Use Access Code to YES and then enter the alpha-numeric code under Access Code. The codes are case-sensitive, so be sure to share this information with the applicable registrants.
On the event webpage, the ticket level will include a note "Access Code Required" with a link to Click here to enter the code.
The code is entered in the new window and the registrant will click Apply. If the code was entered correctly, the window will close and return to the event page where they can now choose the quantity of the event level desired.
If the code entered is incorrect, they will see an error message. The registrant can make additional attempts or click Cancel to return to the event page and choose a different level.