**Yaa Nsia Phillips****Boris**In order to calculate a cost based on selection in a form field ("

**How Many Family Member for Membership**"), you will first have to assign calculation values to items in that form field:http://www.jotform.com/help/301-How-to-Assign-Calculation-Value

Then, you will have to use a

**Form Calculation**field to calculate the total price from the field above:http://www.jotform.com/help/259-How-to-perform-calculation-in-the-form

Finally, you can pass the calculated value to the payment tool for processing by following this guide:

http://www.jotform.com/help/275-How-to-pass-a-calculation-to-a-payment-field

Let us know if you need further assistance in setting it up, and we will be happy to help.

**Boris**Yes, we can help you with conditional logic. As it is another question, it has been moved to a thread of its own:

http://www.jotform.com/answers/760892

We will assist you with conditional logic there, shortly. Thank you.