[Marco van Herwaarden]

There is no option in standard vB to do so. An alternative would be (but this will only work if you have very limited number of forums), is to not allow members to post in your regular forum, but only in a staging forum. In this staging forum people can only see their own posts. Once aproved, a moderator can move the post to the main forum. This will however only work for threads, not individual posts.

Otherwise you will need a modication, i doubt that it will be very difficult to make this.