I am having problem with getting my deposit fee added once the item has been add to cart.

For now I have setup one price (Price+deposit ) together ,and indicated in product this is how much it cost and this is the deposit required.
I would like to have this separate showing Price and once added to cart deposit will kick in

I have created option values, names, and added through attributes controller, the problem I have it is not adding unless I go to select Check box or Radio, or I select by default the deposit fee to be selected but customer can unselected it and they will not be charged deposit

Any ideas how to make it work ?