function isValid(fieldId, fieldName) {
	var field = document.getElementById(fieldId);
	if (field.value == null || field.value == "") {
		alert(fieldName + " is required.") ;
		return false
	}
	return true ;
}


function validate() {
	if (!isValid("name", "Name")) {
		return false ;
	}
	if (!isValid("address", "Address")) {
		return false ;
	}
	if (!isValid("phone", "Phone Number")) {
		return false ;
	}
	if (!isValid("email", "E-mail")) {
		return false ;
	}
	if (!isValid("date", "Appointment Date")) {
		return false ;
        }
	if (!isValid("time", "Appointment Time")) {
		return false ;
	}
	if (!isValid("units", "Number of units")) {
		return false ;
        }
	return true ;
		
}