Zoom Webinar : close registrations 15 min before the start of the training

Hi All,

I need some help. I would like to know if it's possible to close registrations 15 min before the start of the training on Zoom Webinar ? Indeed, some customers register when the training has already begun. It would be more convenient to block registrations.  

Do you know if this functionality is possible?

Thank you, 

Annelise