Hello Simone travaglini,
Sorry for late reply to this,
Do you mean that you only allow this blogger user1, user2, user3 and user4 can publish the blog post right?
If i not getting wrong meaning of your requirement, you can set this 4 blogger under 1 specify user group and write entry/ publish entry set to "YES" (
http://screencast.com/t/xJtglXqVu3 ), then other user group setting write entry and publish entry set to "NO" .
If no, can you elaborate your question with more details, and include a screen shot of what you are referring to? Please advise.