Problem applying discount to shopping cart

[Trondheim1]

I have a shopping cart where certain users should get certain discount....

So I created this "add to cart" button (I only tested this in sandbox):

<form target="paypal" action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post" >
<input type="hidden" name="cmd" value="_s-xclick">
<input type="hidden" name="encrypted" value="value removed">
<input type="image" src="https://www.sandbox.paypal.com/en_US/i/btn/btn_cart_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
<input type="hidden" name="discount_amount" value="10">
<input type="hidden" name="tax_cart" value="25">
<img alt="" border="0" src="https://www.sandbox.paypal.com/en_US/i/scr/pixel.gif" width="1" height="1">
</form>

But no discount is visible in the shopping cart, with that I mean there is no extra ljne in the cart detailing the discount and the price for the item is still the same as without discount, what am I doing wrong?,

Here in this markup I use discount_amount, but have also tried discount_rate_cart without any luck either

info about what fields to use I took from this page in the paypal doc:

https://developer.paypal.com/docs/classic/paypal-payments-standard/integration-guide/Appx_websitesta...

[Trondheim1]

One of the things I had done wrong was that I had checked for adding avanced variables, and took it for granted that they would be applied if I specified them in the button markup....

So I created a new buttton and this time I entered discount in the advanced variable field. No the discount is visible in the shopping cart

But there are issues:

tax_rate was not applieed

As about I had to specify discount on the button, but magine if I had 8000 products, and each product have 8 types of discount, then it would take days to create all the buttons. Isn't there a better option where I specify discount in a input field?

[Trondheim1]

All right, I think I have solved this problem now