<!-- Paste this code into an external JavaScript file named: autoSumCheckboxes.js  -->

/* This script and many more are available free online at
The JavaScript Source :: http://javascript.internet.com
Created by: Jay Rumsey :: http://www.nova.edu/~rumsey/
 */

 function UpdateCost() {
  var sum = 0;
  var gn, elem;
  for (i=0; i<24; i++) {
    gn = 'game'+i;
    elem = document.getElementById(gn);
    if (elem.checked == true) { sum += Number(elem.value); }
  }
  document.getElementById('totalcost').value = sum.toFixed(2);
}