Automatic subdomain for new customers?

Hi all. I am the administrator of a server running the latest cpanel/whm versions on CentOS 6.9. I have a subdomain mycompany.com - I wish to allocate all new clients username.mycompany.com upon signup. This is in addition to any domains they are bringing with them. Is there a way I can do this? I am resisting using mod_dir for security reasons. mycompany.com is owned by another user on the system, so if this presents a problem I am happy to use mycompany2.com Thanks in advance for any help.