Assign Values to Drop-Down Menus in PayPal Third-Party Carts - drop-down-menu

Question

I am trying to implement a PayPal cart on a third-party site. Customers are first asked to select a product ("Product") from a drop-down menu and then, optionally, to enter a specific amount ("Additional Costs") into a text field. Both values should finally be sent to PayPal upon submitting.
While everything works fine with two text fields, where amount_1 and amount_2 are clearly defined, I struggle with assigning different values (/amounts, say 10.00 and 5.00) to the options of the drop down and to make the value of the selected option my value amount_1. Here is the code I figured out so far:
<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_cart">
<input type="hidden" name="business" value="whatever#gmail.com">
<input type="hidden" name="upload" value="1">
<input type="hidden" name="item_name_1" value="Product">
<input type="hidden" name="on0_1" value="Product">
<select name="os0_1">
<option value="product1">Product 1</option>
<option value="product2">Product 2</option>
</select>
<input type="hidden" name="item_name_2" value="Additional Costs">
<input type="text" name="amount_2" value="0.00">GBP
<br>
<br>
<input type="hidden" name="currency_code" value="GBP">
<input type="image" src="http://www.paypal.com/en_US/i/btn/x-click-but01.gif" name="submit" alt="Make payments with PayPal - it's fast, free and secure!">
</form>
option_select and option_amount do not seem to work with this kind of form. Any help would be greatly appreciated!

Answer 1

I'm assuming this is the select box that is used to select the product amount_1:
<select name="os0_1">
<option value="product1">Product 1</option>
<option value="product2">Product 2</option>
</select>
What you need to do is this:
<input type="hidden" name="item_name_1" value="Product" id="item_name_1">
<select name="amount_1" onchange="changeProductName()" id="amount_1">
<option value="5.00">Product that is a fiver</option>
<option value="10.00">Product that is a tenner</option>
</select>
<script>
function changeProductName() {
var e = document.getElementById('amount_1');
var h = document.getElementById('item_name_1');
h.value = e.options[e.selectedIndex].text;
}
</script>
That will change the item_name_1 to the friendly value of the price option.