I have my new users set in the contributor's role as default. I want modification to effect only for the contributor user role, my users when they enter they should be able to post a story, so far so good with Wordpress it works as it should.

. The modification I need done is that my users when they come back and login again in the admin they should be able to post again but only an update to the post and not a new post as it happens by default.
The post that is posted the second time must be appended to the same post that is posted the first time after an horizontal line with title as UPDATE, and consequently there on as many times as he comes back to post, it should only be an update.
The idea is to prevent the user to edit or delete his original post while allowing him to post only an update that append itself to and under the original post.
Nothing Less Nothing More
I will not write easy for the one who know his job because it is none of my business, is it too much I am asking for?
Tell me how much for the job I have described it well I am sure that it does not need any modification to the Databases