function openDateClicked(passID) {
	// disables/enables date and service elements when open dates box is clicked
	// set disabled state to state of checkbox
	state = document.forms["frmBooking"].elements["pass_" + passID + "_open"].checked;
	// loop through form and get service IDs for this pass
	for (x=0; x<document.forms["frmBooking"].elements.length; x++) {
		el = document.forms["frmBooking"].elements[x];
		if (el.name == "pass_" + passID + "_sector_list") {
			sectorID = el.value;
			sectorNumber = document.forms["frmBooking"].elements["pass_" + passID + "_sector_" + sectorID + "_number"].value;
			// found a sectorID, so set the dates' disabled state
			document.forms["frmBooking"].elements["date_" + sectorID + "_day"].disabled = state;
			document.forms["frmBooking"].elements["date_" + sectorID + "_month"].disabled = state;
			document.forms["frmBooking"].elements["date_" + sectorID + "_year"].disabled = state;
			// loop through form looking for services that match this sector ID
			for (y=0; y<document.forms["frmBooking"].elements.length; y++) {
				if (document.forms["frmBooking"].elements[y].name == "pass_" + passID + "_service_" + sectorNumber) {
					// found one, so set its disabled state
					document.forms["frmBooking"].elements[y].disabled = state;
				}
			}
		}
	}
}