var pictures = new Array();

var objCount = 0;

function preload(name, first, second) {  
    pictures[objCount] = new Array(3);
    pictures[objCount][0] = new Image();
    pictures[objCount][0].src = first;
    pictures[objCount][1] = new Image();
    pictures[objCount][1].src = second;
    pictures[objCount][2] = name;
    objCount++;
}

function on(name){
     for (i = 0; i < objCount; i++) {
      if (document.images[pictures[i][2]] != null)
        if (name != pictures[i][2]) { 
          document.images[pictures[i][2]].src = pictures[i][0].src;
        } else {
          document.images[pictures[i][2]].src = pictures[i][1].src;
        }
     }
}

function off(){
     for (i = 0; i < objCount; i++) {
      if (document.images[pictures[i][2]] != null) 
        document.images[pictures[i][2]].src = pictures[i][0].src;
     }
}