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

Code:
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);