Custom message on checkout screen

Hello. Is it possible to add a custom text message on the checkout screen? In my case,

  1. User selects a plan on event details screen.
  2. Clicks buy button.
  3. Completes checkout.
  4. The event details screen needs to refresh in order to show that payment was made. It takes anywhere from 5 seconds to 30 seconds for this to happen. Therefore, it will be helpful to show a text message on checkout screen that tells the user about this delay. It can also prevent duplicate transactions.