Removing an optional Registration field

Hi,
Registering for our event involves a number of optional items which attract an additional charge. This includes an "Early Bird" offer. We implemented the Early Bird offer with List field type, and as a "Fee Field". The options in the list are "$0" and "$120".
After a certain date we want to stop this "Early Bird" option so it is no longer selectable for Registrants.
Since we don't use the Group booking feature I considered setting the "Display In" to "Group Member Form" only. This removed it from the Registration form, and the field was still visible in the "Registrants Manager: Registrants" list. However when I edited the Registrant, it was removed from the edit screen! This is no good if we need to edit a Registrant who has already paid the Early Bird offer.
Is this a bug, or is there a better way to remove paying options from Registrants while keeping them available to administrators?
Thanks.

I was answering another post , and realized that the solution I was proposing there would work for you too. It's still a manual patch (I've been asking for some form of date-regulated custom fields for the past 2 years already), but I think it would work.

Create a CSS class for your website (or for Event Booking in [Configuration -> Custom CSS tab -> Custom CSS] ) such as (if your website template already has a "hide an element" class defined, you could use that instead)
and put that CSS Class name into the [Css Class] field in any custom field that you want to disable for the user, but not on the backend.


Also, turn on the option in the the custom field for [Hide-on-email] so that the user doesn't see the field in their confirmation email.

Oh, and make sure that the custom field is NOT set to REQUIRED, or there will be trouble

Thanks James, I think that will work better than what I am trying to do.
Perhaps an enhancement might be for each field to have a "Hidden" property in the configuration, which will remove the field completely from the input form but still leave it available in all administator forms.
Until then, I will use CSS as you suggest!

Or as @Tuan suggested in that other post:

Tuan Pham Ngoc wrote: Or maybe set access level of the custom field to Special would help
Tuan