I have a way to work around this issue and it gives me what I need, however, I am stuck on the last puzzle.
To accomplish this task, this is what I do:
My Needs:
If subtotal is equal or over $100 then customer can get a free DVD (productid = 2
My solution:
First: add a product free DVD in which I had its productid=28. Make this product hidden but available to sale and give its price is $0.00
Second: Now you need to modify some code.
Open you cart_totals.tpl, add following code at the end of the code:
Code:
{if $cart.display_subtotal >="100"}
Promotion: Your subtotal is $100 or more, you are qualified to receive a FREE DVD. To receive FREE DVD, please
click here to add to your cart.
{/if}
With the code above, when you customer view cart, if suborder is over or equal $100, then above message will display. If it is display, you customer need to click on this link to add free DVD to cart.
Now open you product.tpl, modify your code so that productid=28 display price is FREE, and quantity you can make it hidden to value 1. So when you customer click on add to cart for this product, it will add to the cart with quantity is 1 and price is $0.00.
Now open you cart.tpl and modify it so that you won't let your customer change the quantity of productid=28.
This should give you what you need for if buy x$x.xx then get y item forfree. However, when I got to this step, I got stuck ont he last step, that if customer decides to change the quantity of items in the cart to less than $100, then the free DVD is still in the cart.
Does any know show to solve this? If I could code to make the page automatically remove free DVD item out of the cart as soon as subtotal is less than $100. Then my whole puzzle is completed.