Only registered users can Add to cart

[digitalglobe]

Hi to all 
I want to be able to restrict the website that only registered users can Add to cart products .
Just like it is possible in older VM versions.

As it is now, I can remove the pricing for unregistered users, but they can still "Add to Cart", and view the cart information... In which they will find the prices not shown on the products.

Pls help me 

Thx a lot

[spider2]

Yes I want it too. How can we do that?