Loaders = new Array;

for(var i=0;i<PicName.length;i++) {
  Loaders[i]=new Image;
  Loaders[i].src=PicName[i]+"-a."+PicExts[i];
  Loaders[i+PicName.length]=new Image;
  Loaders[i+PicName.length].src=PicName[i]+"-c."+PicExts[i];
}

function Roll(DocNo,ImgName,State,Message) {
  var PicIndex;
  for(PicIndex=0;PicName[PicIndex]!=ImgName;PicIndex++);
  if(State)
    PicIndex+=PicName.length;
  document.images[DocNo].src=Loaders[PicIndex].src;
  window.status=Message;
}