function contractall(){
if (document.getElementById){
var inc=0
while (document.getElementById("ventana"+inc)){
document.getElementById("ventana"+inc).style.display="none"
inc++
}
}
}

function expandone(){
if (document.getElementById){
var selectedItem=document.ventanaform.ventanaoption.selectedIndex
contractall()
document.getElementById("ventana"+selectedItem).style.display="block"
}
}

if (window.addEventListener)
window.addEventListener("load", expandone, false)
else if (window.attachEvent)
window.attachEvent("onload", expandone)