Set up Google distance matrix in Fabrik form element on Joomla

On Fabrik form I have 2 dropdown fields. [login to view URL] and 2.End. I want to use the values of the fields to calculate the driving distance between the 2 points then save that value to the record field in the database. Prefereably using the Fabrik calc element so that it uses AJAX but using js with an on change trigger may also work. I have completed the js and tested working on plain html page but need someone with Fabrik/js/AJAX knowledge to help me finish it.