Single Use Custom Field?

Is it possible to make a single use custom field?

I want to create specific slots for user registration, so like a drop down menu with:
Slot 1
Slot 2
Slot 3
Slot 4
ect.

Is there a way to automatically delete or make a selection show inactive (or change the color of selection) once another user has registered?

I am using Joomla 2.5.19, Community Builder 1.9.1 and Event Booking 1.4.5

Sorry Hanson but this feature is not supported in the extension.

Regards,

Tuan