function cascadingMenu(num)
{
	var obj = "obj"+num;
	var img = "img"+num;

	/* mets à "none" si la valeur est nulle */
	if (document.getElementById(obj).style.display == null)
		document.getElementById(obj).style.display = "none";

	if (document.getElementById(obj).style.display == "none")
	{
		document.getElementById(obj).style.display = "block";
		document.getElementById(img).src = "/img/minus.gif";
	}
	else
	{
		document.getElementById(obj).style.display = "none";
		document.getElementById(img).src = "/img/plus.gif";
	}
}