Functionality question – limited seats

Hi, I want to have a sign up form for a conference. There are limited seats. So I would like options in the contact form, that will only show as long as there are still seats available.

When a number of people have signed up and an option is full, I want this option to not show in the Contact form. Can I do that somehow?

Example: Have 100 Gold seats, 50 Silver seats and 20 bronze seats. When 100 people have signed up for the gold seats, this option should disappear in the contact form. But the silver and bronze seats should still be show until they have been taking.