开源 舆情监控:求助 这段代码怎么改？

我想让下面这段显示图片的代码能够显示一个文件夹里的所有的图片该怎么改啊？（以后只要在文件夹里添加图片就可以了）

<SCRIPT language=JavaScript>

// Set slideShowSpeed (milliseconds)
var slideShowSpeed = 2000;
// Duration of crossfade (seconds)
var crossFadeDuration = 3;
// Specify the image files
var Pic = new Array();
// to add more images, just continue
// the pattern, adding to the array below

Pic[0] = '/a/1.jpg'
Pic[1] = '/a/2.jpg'
Pic[2] = '/a/3.jpg'
Pic[3] = '/a/4.jpg'
Pic[4] = '/a/5.jpg'

// do not edit anything below this line
var t;
var j = 0;
var p = Pic.length;
var preLoad = new Array();
for (i = 0; i < p; i++) {
preLoad[i] = new Image();
preLoad[i].src = Pic[i];
}
function runSlideShow() {
if (document.all) {
document.images.SlideShow.style.filter="blendTrans(duration=2)";
document.images.SlideShow.style.filter="blendTrans(duration=crossFadeDuration)";
document.images.SlideShow.filters.blendTrans.Apply();
}
document.images.SlideShow.src = preLoad[j].src;
if (document.all) {
document.images.SlideShow.filters.blendTrans.Play();
}
j = j + 1;
if (j > (p - 1)) j = 0;
t = setTimeout('runSlideShow()', slideShowSpeed);
}
</SCRIPT>