normal_image = new Image();
normal_image.src = "zcode/images/tri_grey_empty.png";

mouseover_image = new Image();
mouseover_image.src = "zcode/images/tri_grey.png";

function swap()
{
  if (document.images)
  {
    for (var x=0; x < swap.arguments.length; x+=2) 
    {
      document[swap.arguments[x]].src = eval(swap.arguments[x+1] + ".src");
    }
  }
}