var pageLoaded;

pageLoaded = false;

function makePics (howMany) {
  howMany = Math.abs (howMany);
  naviA = new Array (howMany);
  naviB = new Array (howMany);
  pageLoaded = true;
  for (var i = 0; i < howMany; i++) {
    naviA[i] = new Image();
    naviA[i].src = "kuvat/valikko_nav_" + (i + 1) + "_off.png";
    naviB[i] = new Image();
    naviB[i].src = "kuvat/valikko_nav_" + (i + 1) + "_on.png";
  }
}

function imageOn (number) {
     if (pageLoaded) {
       document.images["MenuNav" + number].src = naviB[number - 1].src;
    }
}

function imageOff (number) {
    if (pageLoaded) {
    document.images["MenuNav" + number].src = naviA[number - 1].src;
    }
}