How to notify specific users when i'm posting/modifying a new post

Hello everyone,

Here’s what I’m trying to do…
I’m trying to send new submissions only to contractors requested. Using Role Scoper, I can select only users who can access the new submission. However, I am looking for a way to notify users via email when a new submissions is placed online. I can not make “groups” because it is not specific groups but strategically chosen when a new submissions is placed online.

After a long search, I ask you, how can I sent an email to registered users. Ideally I would like to have the option to select users directly in the article as Role Scoper does.