If you want to exclude posts from a particular category then you could try putting this in your functions.php

function exclude_posts_from_category( $query ) {
    $catname = "Put you category name here";
    if ( $query->is_category() && ( $catname == $query->query_vars['category_name'] ) ) {
        $query->query_vars['post__not_in '] = array( 1, 2, 3 );
    }
}
add_action( 'pre_get_posts', 'exclude_posts_from_category' );

You can use $query->query_vars['post__in '] = array( 1, 2, 3 ); in case you want to specify the posts that should be included ( It will only include the post id you mention and if they are in the current category ).