var n

function preloadImages() {
if (document.images) {
var imgFiles = preloadImages.arguments;
var preloadArray = new Array();

for (var i=0; i<imgFiles.length; i++) {
preloadArray[i] = new Image;
preloadArray[i].src = imgFiles[i];
}
}
}

function pic(nam,but){
if(!but){document.images[nam].src=n}
else {
n=document.images[nam].src 
document.images[nam].src=but
}
}