How to add additional price to Item price

Hello, am using the paypal + stripe contact form 7 plugin and it is awesome. However I have a bit of a problem. I want my visitors to select one or more products according to which the price should change. For example there are 3 services/products to choose from. So if the visitor selects 2 of the services/products, the price should automatically add to the base service. Is this possible? Thanks in advance.