SQL permissions to create NAV windows logins

Hi all,

I want to delegate creating windows logins in Dynamics NAV (currently 2009 R2 Classic) to several key users in our company but I don't want to assign the SQL database role db_owner or server role sysadmin to the users.

I've made several tests with an user account and I got it worked with the database role db_accessadmin instead of db_owner but not without the server role sysadmin. Does anyone have a hint or an idea, what I could do to grant those users only for creating, modifying and deleting windows logins via Dynamics NAV without giving them the sysadmin permission?

Thanks in advance!