normal_image = new Image();
normal_image.src = "http://www.maxburst.com/images/requestquote.gif";

mouseover_image = new Image();
mouseover_image.src = "http://www.maxburst.com/images/requestquote_over.gif";

<!-- repeat the 4 lines above for any subsequent images. -->

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");
   }
}
}