var image_count = 0, 
    lock = false,
    images_needed = 0;

function initialize(count) {

    images_needed = count; 

}
function count_images() {

   if (++image_count == images_needed) {
      lock = true;
   } 

} 
function changeImage(name, newsrc) {

   //if (lock) {
      document.images[name].src = newsrc;
   //} 
   
   
}