ASPdotnetStorefront C# Modification

Very simple modification to my [login to view URL] display page written in C#. I have an aspdotnetstorefront that that we just wanted to ask the customer on the shopping cart page if they want recurring shipments. If they do not check the box then nothing changes but if they do check the box then we would need to change the variant ID for the product in the cart. Each of my products has two variants. One that is just a one time shipment and another that is recurring. So to sum it up on my cart page I wanted to give the customer the opportunity to choose recurring shipments by checking a checkbox. If checkbox on [login to view URL] page is checked then we need to switch the variant for the product in the cart. Please only C# experts Thanks