integrated paypal form - want to apply coupon

[njdirt]

Hello,

  I am working on applying a coupon code option to a Paypal integrated store html page on my website.  I want the user to have the ability to enter a Coupon Code for a discount on each item.  I pirated some sample how-to code from a site (sorry I don't have the info), but I think the fact that I have multiple items listed on the page prevents it from working.  I've posted the relevant code below.

 

I think the problem may be in the assigning of the discount_rate variable where I use 'document.contra.discount_rate.value = "10"; 

 

Total JS noob too so I'm trying to figure it out as i go.  Thanks in advance!

 

<form name="contra" method='POST' action='https://www.paypal.com/cgi-bin/webscr' target='paypal' onSubmit="paypal=window.open('https://www.paypal.com/cgi-bin/webscr','paypal','width=680,height=400,status=yes,location=no,menubar=no,scrollbars=yes,resizable=yes');paypal.focus();" >
<input type="hidden" name="business" value ="xxxxx"> 
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="cmd" value="_cart"> 
<input type="hidden" name="add" value="1">
<select name='os0' size='1' style='background-color: #FFFFFF; color: #000000;'>
<option value='Select Top Tube'>Select Top Tube</option>
<option value="21.5"">21.5"</option>
<option value="22"">22"</option>
</select>
<input type='hidden' name='on0' value='Top Tube'>
<select name='os1' size='1' style='background-color: #FFFFFF; color: #000000;'>
<option value='Select Color'>Select Color</option>
<option value='Black'>Neon Green</option>
<option value='Brown'>Dark Orange</option>
<option value="Orange">Black</option>
</select>
<input type='hidden' name='on1' value='Color'><br><br>Qty <input type='text' name='quantity' size='3' value='1'> <input type='submit' onclick='if(os0.selectedIndex==0){alert(os0.options[0].value);os0.focus();return(false);}if(os1.selectedIndex==0){alert(os1.options[0].value);os1.focus();return(false);}' value='Add to Order' name='B1' style='background-color: #ff6600; color: #000000; font-weight: bold'>
 <input type='submit' value='View Order' name='display' style='background-color: #ff6600; color: #000000; font-weight: bold'>
<!-- promo code -->
<br>
<input type="text" name="promo">     <input type="button" value="Check It" name="Submit" onclick=javascript:validate(promo.value,"GOLD10") > 
<script language="javascript">
function validate(text1,text2) { 
if (text1 == text2)
{
window.alert("Nice, you get a 10% Discount!");
document.contra.discount_rate.value = "10";
document.contra.discount_rate2.value = "10";
document.contra.on3.value = "Coupon Entered";
document.contra.os3.value = "GOLD10";
}
if (text1 !== text2)
{
window.alert("Sorry, No Discount!");
}
}
</script>
<!-- end promo code -->
<br><br><noscript>Please enable Javascript to order this item</noscript><input type='hidden' name='item_number' value=''>
<input type='hidden' name='item_name' value='MOB'>
<input type='hidden' name='amount' value='399.99'>
</form>