var theOffImage = new Image;
var theOnImage = new Image;

theOffImage.src = "..\images/minitwirl2.jpg";
theOnImage.src = "..\images/minitwirl.jpg";

function rollOn(mini){
 document[imagename].src = theOnImage.src;
}

function rollOff(mini){
 document[imagename].src = theOffImage.src;
}