Remove choices from look up field when selected

Remove choices from look up field when selected

I am a real novice when it comes to code so I just thought I would say that up front.  Is there a way to remove an item from a lookup field once it is selected by the user.  I want to limit the number of people that can register for an event so I thought I would create a form that has seats numbered from 1-10.  When they pick a seat the "1" would be removed then the "2" and so on until there are no seats left.