function Start() {
  var t = 31; // interval in seconds
  image = "http://www.werkgroepslechtvalk.nl/images/live-beelden/cb1.jpg"; //name of the image

  tmp = new Date();
  tmp = "?"+tmp.getTime();
  document.images["refresh"].src = image+tmp;
  setTimeout("Start()", t*1000);
}

function Start2() {
  var t = 31; // interval in seconds
  image = "http://www.werkgroepslechtvalk.nl/images/live-beelden/cb2.jpg"; //name of the image

  tmp = new Date();
  tmp = "?"+tmp.getTime();
  document.images["refresh2"].src = image+tmp;
  setTimeout("Start2()", t*1000);
}