function tally(form) {
var total = 0;
var max = form.checkbox.length;
for (var idx = 0; idx < max; idx++) {
if (eval("document.playlist.checkbox[" + idx + "].checked") == true) {
    total += 1;
   }
   var geekpercent = [total/max*100]
}
alert("You are " + geekpercent + "% geek");
}