I want to make a module for Magento 1.X to set discount when customer in Category A selected a product. whwn customer select product in category B. which have a discount for item of category B only.
For example, Customer select product(X) $4 in category A. who select product(Y) $10 in Category B
If I set 30% off discount
So I want the result in cart is
product (Y) $7
Can it work?