Oops, I noticed at the last second that you don't want users 5-10
to post to the list, either.  Try setting up the list as an edited
list, and make users 1-4 editors:
 
* Send= Editor
* Editor= User1@HisNode
* Editor= User2@HerNode
* Editor= User3@ItsNode
* Editor= User4@SomeNode
 
If a user who isn't defined in an "Editor= " section tries to post,
his post goes directly to the first editor, who for all practical
purposes should be the list owner.
 
HTH.