list_choix = {
"2006" : ["January", "February", "March", "April", "May"],
"2005" : ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"],
"2005" : ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]
}

function ajout(selection){
	nb_select = selection.parentNode.getElementsByTagName("select").length;
	if ( selection == selection.parentNode.getElementsByTagName("select")[nb_select-1] ) {
		element_select = selection;
		selection = selection.options[selection.selectedIndex].value;
		if ( list_choix[selection] ) {
			new_liste = document.createElement("select");
			element_select.parentNode.appendChild(new_liste);
			new_liste.setAttribute("id", "choix"+nb_select);
			new_liste.setAttribute("name", "choix"+nb_select);
			new_liste.setAttribute("onchange", "ajout(this)");
			for (var i=0; i<list_choix[selection].length; i++) {
				new_option = document.createElement("option");
				new_liste.appendChild(new_option);
				new_option.setAttribute("value", list_choix[selection][i]);
				new_option.text = list_choix[selection][i];
			}
		}
	}
	else {
		selection.parentNode.removeChild(selection.nextSibling);
		ajout(selection)
	}
}