3-in-a-row

<div id="recent-projects">
                <?php
            $count = 0;
            $recentblog = new WP_Query();
            $recentblog->query("category_name=parent-category");
            while($recentblog->have_posts()) : $recentblog->the_post()
        ?>

        <div class="project-box<?php if( $count%3 == 0 ) { echo '-1'; }; $count++; ?>">
                <a href="<?php the_permalink(); ?>"><img src="<?php $thumb = get_post_custom_values('portfolio-image'); echo $thumb[0]; ?>" alt="<?php the_title(); ?>" />
                <h4><?php the_title(); ?></h4></a>
        </div>

         <?php endwhile;
        ?>
</div><!--end recent-projects-->