Template Tags/next post link

Template Tags/next post link usage is this:

<?php next_post_link(‘format’, ‘link’, ‘in_same_cat’, ‘excluded_categories’); ?>

I choose to displays custom text as link to the next post within the same category as the current post. The problem is this:
I choose category “X”,
I open one post from this category
The next post is from the same category, this is OK but on index page I have lastest posts from diferent category; from here if I enter on one post and then I click “next post” its not from lastest post but from same category and this is not OK. From index user must navigate in lastest post not only in one category.

Sorry for my bad English