Require Seller confirmation before payment processed

Products in several categories (e.g. paintings) in my cart will require significant handling/shipping costs. How can I force the checkout process to initiate email contact, or suggest phone contact with the seller who could then determine the specific shipping / handling cost for the product? Or is there a way to prevent the product from being added to the cart by the buyer in the first place but still have the product on view in the cart for consideration by buyers?

I could probably include special instructions in the category description, or a new topic in the information block to explain that the seller should be contacted directly due to special shipping requirements. But I still would need to display the products in the cart.

Probably a very simple solution here, but my mind is just not working tonight.

Thanks,
David

My question focused on shipping, since that's where I have a need, but it could be approached more broadly. How can I set up a product so that it cannot be purchased through the cart, but will still be shown to the buyer for his consideration? In the category/product description I can advise the buyer to contact the store directly to purchase the item since special handling and shipping will be required and a price including those cost components cannot be calculated within the cart.

Thanks in advance for any suggestions.

David