Question about hooks

Hi guys,

Is there some possibility to run the hooks before the account or domain name is created/added ?

I want to create a module/plugin (not sure how you call it here ) to block account creation and domain name/subdomain adding in case the username or domain name/subdomain is listed in some list managed by the server administrator so the users won't be able to add the domain names like "gmail.com", "hotmail.com", etc as the main domain names or addons of their accounts .

Thanks.