var main_id = new Array();
var main_title = new Array();
var second_id = new Array();
var second_title = new Array();
var third_id = new Array();
var third_title = new Array();

//預設資料
main_id[0] = 1;
main_title[0] = "鐵道旅遊";
second_id[1] = new Array();
second_title[1] = new Array() ;
main_id[1] = 2;
main_title[1] = "巴士旅遊";
second_id[2] = new Array();
second_title[2] = new Array() ;
main_id[2] = 3;
main_title[2] = "國內旅遊訂房";
second_id[3] = new Array();
second_title[3] = new Array() ;
main_id[3] = 4;
main_title[3] = "航空公司自由行";
second_id[4] = new Array();
second_title[4] = new Array() ;

var pro = this.document.forms["CruiseBlock"];

pro.topic1.length = (main_id.length+1);
pro.topic1.options[0].value = "";
pro.topic1.options[0].text = "----";

for(var i=1; i<=main_id.length;i++){
	pro.topic1.options[i].value = main_id[(i-1)];
	pro.topic1.options[i].text = main_title[(i-1)];
}

SelMain();

function SelMain(){
	if( pro.topic1.value != ""){
		pro.topic2.length = (second_id[pro.topic1.value].length+1);
	}else{
		pro.topic2.length = 1;
	}
	pro.topic2.options[0].value = "";
	pro.topic2.options[0].text = "----";
	
	for(var i=1; i<pro.topic2.length; i++){
		pro.topic2.options[i].value = second_id[pro.topic1.value][(i-1)];
		pro.topic2.options[i].text = second_title[pro.topic1.value][(i-1)];

		if(i==1){
			pro.topic2.options[i].selected = true;
		}
	}

	SelSecond();
}

function SelSecond(){
	if( pro.topic2.value != ""){
		pro.topic3.length = (third_id[pro.topic2.value].length+1);
	}else{
		pro.topic3.length = 1;
	}
	pro.topic3.options[0].value = "";
	pro.topic3.options[0].text = "----";

	for(var i=1; i<pro.topic3.length; i++){
		pro.topic3.options[i].value = third_id[pro.topic2.value][(i-1)];
		pro.topic3.options[i].text = third_title[pro.topic2.value][(i-1)];

		if(i==1){
			pro.topic3.options[i].selected = true;
		}
	}
}