function isEmail(field_id) {
	var field = eval(doc + field_id + doc2);
	
	var error_msg = eval(doc + field_id + '_error_msg' + doc2);
	var error_field = eval(doc + field_id + '_field_error' + doc2);
	var error_msg_txt = eval(doc + field_id + '_field_error_msg' + doc2);
	var required_field = eval(doc + field_id + '_required' + doc2);	

	if (required_field.value == "Y") {
		if (field.value.indexOf('@') == -1 || field.value.indexOf('.', field.value.indexOf('@')) == -1) {
			error_msg.innerHTML = "Invalid E-mail address";
			
			error_field.value = "Y";			
		} else if (!field.value || field.value.replace(/ /gi, "").length == 0) {
			error_msg.innerHTML = error_msg_txt.value;
			
			error_field.value = "Y";
			
			field.value = "";
		} else {
			error_msg.innerHTML = "";
	
			error_field.value = "N";
		}
	}
}