Wordpress Woocommerce

i'm using Woo commerce with WC Vendors plugin which turns Woo commerce into a multi vendor shop and allows users to add products from several vendors to the check out cart and I need to add the ability for customers to be able to pay a " gratuity/tip fee" for each vendor transaction, in other words if the user sends 3 items to the cart from a different vendors then a field needs to be made available for each of the vendors to input 'gratuity/tip fee" amount Example Usage: Add a Gratuity/ Tip for each vendor. ___________________________________________ Choose: Delivery | Carry out (if "Carry out" is chosen only cash option is made available below) Choose: Cash | Paypal (below here is only available if Paypal option is chosen) Vendor 1: None | 5% | 10% | 15% | 20% | 25% | text box option ---------------------------------------------- Vendor 2: None | 5% | 10% | 15% | 20% | 25% | text box option ---------------------------------------------- Vendor 3: None | 5% | 10% | 15% | 20% | 25% | text box option ________________________________________ The gratuity amount chosen for each vendor must be defined in WC Vendors purchase order email sent to both vendors and customers. i will select lower bid