How to assign calculation values to a field ?

Hi
*How do I add various money value fields that when selected add to the
overall total *
*I want customer to select options as they progress the order form*
i.e.
Question : please select your preferred registered office:
London £50
Manchester £40
Glasgow £25
*Once selected the amount is then added to the cart*
Questions : Do you require Mail Forwarding?
Yes - £90
No - £0
*Once select the amount is then added to the cart*
so on and so on, some of my forms offer 20 or 30 options as they progress
the order form, i.e add a nominee director, registered office, printed
documents, VAT registration etc.
Please view this form as an example
https://fs20.formsite.com/foerster/form70/index.html
Many Thanks William

Hi,

You can assign calculation values to your fields, just follow this guide : http://www.jotform.com/help/301-How-to-Assign-Calculation-Value 

Then you can use this guide to perform calculation in your form : http://www.jotform.com/help/259-How-to-perform-calculation-in-the-form 

And this is the link to the widget : http://widgets.jotform.com/widget/calculation 

You will find how to send the calculated value on this guide : http://www.jotform.com/help/275-How-to-pass-a-calculation-to-a-payment-field 

Do let us know if you need more help, we will be glad to assist you.

Regards.