and on the whole 1,2 not 3 then not 4 and 5.

perhaps it would be better to have 4 and 5 anyway listed in the thread if it is known 4 and 5 refer to 1 and 2 (i assume so???). then if and when 3 comes along it can be added in to the thread using the date system.

It might be possible to actually create a post saying:

"sorry, this post is unavaliable" in place of post 3. If post 3 then comes along then add it in.

A situation may happen when someone posts post 3 and then deletes it (i think you can do this can't you) or if it gets deleted by someone else for spam or any other reason and it is a shame for one mucked up post to prevent the whole thread being downloaded.

This assumes that post 4 and 5 refer to post 1, 2 and 3 but i think they do as this is the many to many thing you were talking about for usenet_ref i think so it should work.

I am learning this whole usenet system as we go along so sorry if making mistakes.