[Dan]

Simple!

<script language="Javascript">
<!--
//Slide Show script (this notice must stay intact)
//For this and more scripts
//visit java-scripts.net or http://wsabstract.com

if (document.images) {
     button1 = new Image
     button2 = new Image

     button1.src = 'img1.gif'
     button2.src = 'img2.gif'
 }
//-->
</script>

Obviously you can edit the values above to match your requirements.