Paypal Buy it Now AS2 help

[Izlude]

I've a few question. Before making my flash paypal buy it now button, do I have to make the actual button (for an item I want to sell) on the paypal website itself first so the flash button connects to it?

Second, I'd like to have it coded in AS2 if possible. I found this AS3 version, I have no problem using it if I must (just change my shop.swf to be AS3) which I hope doesn't break some functionality...

Here's the code, but my question about it is that I want my shipping to be $3.50, so would I change no_shipping = "2" to shipping = "3.50" ?

Item Number.. where would I get one?

Thanks for your patience

function buyNowDown(event:MouseEvent):void { 

 var url:String = "https://www.paypal.com/cgi-bin/webscr";
 var payPal:URLRequest = new URLRequest(url);
 var variables:URLVariables = new URLVariables();
 variables.cmd = "_xclick";

 variables.business = "me@mysite.com";
 variables.item_name = "product name";
 variables.item_number = "123456";
 variables.amount = "10.00";
 variables.no_shipping = "2"; 
 variables.no_note = "1";
 variables.currency_code = "USD";
 variables.lc = "US";
 variables.bn = "PP-BuyNowBF"; 

 payPal.data = variables;
 payPal.method = URLRequestMethod.POST;
 navigateToURL(payPal, "_self"); // Same window method, no popup(recommended)
}

 buyNow_btn.addEventListener(MouseEvent.CLICK, buyNowDown);

[Izlude]

I found it but I still have 1 last question (I got the following code from a dead link through archive org where links today were dead).

What you see below is ActionScript2, tested and working.. My question is, am I able to add a "stock number"? (how many of that product that is available). What might the var string be?

var cmd:String = "_xclick";

var business:String = "paypal email here";

var item_name:String = "product name";

var item_number:String = "make your own product number or leave blank";

var amount:String = "price";

var shipping:String = "shipping price";

var no_note:String = "1";

var currency_code:String = "USD";

var lc:String = "US";

var bn:String = "PP-BuyNowBF";



buynow_btn.onRelease = function() {

	getURL("https://www.paypal.com/cgi-bin/webscr", "_blank", "POST");

};