var activeSubMenuId = 0;

function sw_submenu(id) {
	// vorige menu sluiten
	if (activeSubMenuId > 0) {
		document.getElementById("sub_" + activeSubMenuId).style.display = 'none';
	}
	
	// actieve menu openen
	obj = document.getElementById("sub_" + id);
	obj.style.display = 'block';
	
	// nieuw active menu zetten
	activeSubMenuId = id;
}