Copy quantity discounts froma a product to a category

[7inter]

Well, I need to introduce a lot of products with different prices depends on the quantity that clients order and I need that clients can see the discounts like they're showed on product info page when you've set up discounts from products price manager on admin.
I decide to explore following files:
admin/attributes_controller.php
admin/includes/functions/general.php
in attributes_controller.php you can find the code for copy attributes from one product to another product or a category, I've copied this code and pasted it on
admin/products_price_manager.php and I've modified it and all the forms show it on the admin>catalog>Products Price Manager
but I don't know how to modify the functions in order to make it work ok.
The functions I think must be copied and modified are:
zen_copy_products_attributes
zen_products_id_valid
zen_has_product_attributes
to
zen_copy_products_discounts
zen_products_id_valid
zen_has_product_discounts
I upload now the products_price_manager.php that I've modified praying if someone can help me to solve this need please.
Sorry for my english because I'm from Spain and I know my english is not as good as I would desire. Thanks for your attention.