Creating an interactive map with two filtering levels and distance information

Dear all, 

I would like to create a map chart where we can visualize first the number of alerts by city and then, once I choose a given city, visualize all the manufacturing sites that purchase materials from the supplier in this city and their relative distances to this city ... The first part of the question is straightforward but how can I implement the second part? 

Thank you in advance ,


(1) Answer