Hi to all!!!

Im using zen cart 1.8, im a newbie in this kind of software, my question its about special offers, i want to sell e-books in zen cart store, whole process that i want to develop im going to explain next:

As i told i want to sell e-books, this process its easy in zen cart, and i want to add a special offer that consist in:

* Customers who want to purchase an e-book also have the option to get 50 additional ebooks for $20 dollars or any price before they make the purchase, I want them to choose any
e-book that they want from a database of 500 e-books but only can choose 50, this means that the customer will pay a price for the e-book plus the price of the 50 additional e-books in one step.

Can i do this process in zen cart??

Please somebody help me with this issue

Thank You!!!