function collapse(v,p) {

  e = document.getElementById(v);

  if (e.style.display == '') {
    e.style.display = 'none';
    eval('document.' + p + '.src= "images/img.nwSet/knoppen/pijl.gif"');
  } else {
    e.style.display = '';
    eval('document.' + p + '.src= "images/img.nwSet/knoppen/pijl_02.gif"');
  }
  return false;
}