Using Javascript To Loop Images??

Let's say I have a Javascript function that loops over and over. In
that function i have it alternating images on a button this way:

if(var==0){
var myHTML = "<input type='button' style='background-image:
url(grnbutt.jpg);etc. etc.'>";
var outq = document.getElementById("qbutt");
outq.innerHTML = myHTML;
}
else{
var myHTML = "<input type='button' style='background-image:
url(grnbuttdark.jpg);etc. etc.'>";
var outq = document.getElementById("qbutt");
outq.innerHTML = myHTML;
}

This works great using Firefox, and works with Internet Explorer also
EXCEPT if its set to "Check for newer versions of stored pages: Every
visit to the page". With that setting, IE will download those 2 images
from the server every single time through the loop. So then I tried
putting both images on the same jpg and then moving the image:

if(var==0){
var elem = document.getElementById("grn");
elem.style.backgroundPosition = "-100px 0";
}
else{
var elem = document.getElementById("grn");
elem.style.backgroundPosition = "center";
}

This also works, but also, constantly downloads new images when using
IE with the above setting. Microsoft calls this a "feature". They then
offer a fix for this "feature" that... doesn't work. Preloading
doesn't work. Loading the 2 images in a <divset to invisible doesn't
work. I've tried suggestions of creating php files that tell the
browser that the images don't expire for years. That didn't work for
me. Many people have also suggested that there is no way around it...
it can't be fixed until Microsoft fixes it.

So, is there any javascript way to loop 2 images on a button, without
Internet Explorer constantly downloading those 2 images over and over,
when its set to "Check for newer versions of stored pages: Every visit
to the page"?