nth-child() - sets of 4?

nth-child() - sets of 4?

I'm using this function in my navigation:
  2. $(document).ready(function(){
  3. $('ul.tabNav a').click(function() {
  4. var curChildIndex = $(this).parent().prevAll().length + 1;
  5. $(this).parent().parent().children('.current').attr('id', 'idle');
  6. $(this).parent().parent().children('.current').removeClass('current');
  7. $(this).parent().addClass('current');
  8. $(this).parent().attr('id', 'current');
  9. $(this).parent().parent().next('.tabContainer').children('.current').slideUp('fast',function() {
  10. $(this).removeClass('current');
  11. $(this).parent().children('div:nth-child('+curChildIndex+')').slideDown('normal',function() {
  12. $(this).addClass('current');
  13. });
  14. });
  15. return false;
  16. });
  17. });
I have 16 divs in the container and 4 menu buttons - I'd like to reveal 4 subsequent sibling divs at a time. 
I've tried this:
  2. $(this).parent().children('div:nth-child('+curChildIndex+')').nextUntil('section','div').slideDown('normal',function() {
  3. $(this).addClass('current');
...with empty <section></section> elements as dividers, but it isn't working because it is apparently always counting from the start and not the curChildIndex var as I expected. (I obviously did not write the function.)
Suggestions on how to make it work?