Retrieve numbers from multi-fields & multi-lines lookups for calculation

Retrieve numbers from multi-fields & multi-lines lookups for calculation

Hello.

I have a form with 2 lookup field that are multi-fields for ease of choice by the customer :

First lookup (SUBSCRIPTION) looks like this : Montréal - Thuesdays -  $600.00 (only one choice possible)
Second lookup (OPTIONS) looks like this : Eggs - $60.00 (more than one choice possible with radio buttons)

I want to retrieve all dollars amount to calculate the total of the invoice, keeping in mind that second lookup may have more than one option selected with radio buttons.

I have no idea where to start...

Sylvain