Build an Online Store

I have a b2b site developed on Open Cart. I want you to write a module,which will show a campaign page, where we will add monthly campaigns. campaigns are like this. *Buy 12 pieces from some category/subcategory get 1 free from these category/subcategory, *Buy 100$ from some category/subcategory and get 1 piece free from these category/subcategory. *Buy 5 pieces of 1234(productid), 5 pieces of 22222(productid), 5 pieces of 33333(productid), 5 pieces of 44444(productid), and get 1 piece 1234(productid) and 1 piece of 6666(productid) free and 1 tester this campaign page should word in one of these 2 ways. [login to view URL] campaigns should list as an image and text in campaign page, and when I click "add to cart" that products listed in campaign should go to basket. [login to view URL] campaign calculation should be calculated in basket. for example, if I buy 12 pieces from some category/subcategory then 1 more should be placed in basket for free automatically.