Thanks for all the input so far; I am using the PostSecurity extension as modified by JP. This allows me to set an internal secure category that you must be logged in to view. It works great..
The next issues are these
1) I am using a category list widget. I only want this to show up if the user has see the posts.
2) If you scroll through the posts , and the next post is "Secure Post", the post serving function Redirects to the error404 page
3) If you use the internal blog search it does find the post and gives a preview of the post.
I am not an accomplished c# & .net developer so before I start to hack the relevant code to solve these, does anyone have any elegant solutions for this.
Thanks in advance