img1 = new Image();
img1.src = "images/menu_back1.gif";

img2 = new Image();
img2.src = "images/menu_back2.gif";

function menuOver(id) {
   eval('menu'+id+'.background="images/menu_back1.gif";');
}

function menuOut(id) {
   eval('menu'+id+'.background="";');
}

function menuOver2(id) {
   eval('menu'+id+'.background="images/menu_back2.gif";');
}

function menuOut2(id) {
   eval('menu'+id+'.background="";');
}