Multisite in shared host; cpanel in separate db and shared user table

Dear Friends,
I have a drupal website in hostgator's shared host. It has cpanel. I can park or point many domains in my host.
I'd like to install other drupal websites with separate database and shared user table.
Unfortuantely i couldn't find a topic which would be justified with my requirements.
Could you please describe me about it or refer to other suitable topic?
Thanks