Add to cart with +- buttons

[sandomatyas]

I want to build a small webshop which sells only 6 products.
The idea would be to display all of the products with a category layout, every product has title, short desc, image, price and a quantity box with +- buttons, but without addtocart button. When the customer clicks on + VM should add 1 product to the cart. When clicks + again, the cart should contain 2 of this product. When clicks - the quantity should be reduced.
There should be a "total amount" field and a simple "go to checkout" button at the bottom of the page.
Any idea to do that?
I'm familiar with js/php