Locking online Excel cells based on checkbox true/false value

Hi there, I've been asked to create an online booking sheet for a colleague who dispatches trucks. He wants to send this to the wider business and have people be able to update it with scheduled works. Once they have confirmed the work, it will pull into another sheet for him to do some additional work.
He doesn't want people to be able to change their booking after they have confirmed it, otherwise trucks get sent to places only to get turned away etc.
Because he wants this online, I'm limited in my solutions. I've attached screenshots of desktop Excel with my attempt. https://imgur.com/a/DZmgsWf.
I've tried to solve this via data validation rules but can't quite get it to work. If the checkbox has been ticked then it can't be unticked, nor can the data be edited. So that's good.
The problem is that you can simply delete the cells if you want. Does anybody know a way to prevent cell contents from being deleted based on data validation rules, or once data has been entered?
Thanks