You can go for distance calculation between two locations using calculated field. Here is the link:
Then try to apply filter on this calculation.
Hope this will help you.
Thank you for your quick response.
I thought about that too, but I don't know if it's an option because of the number of customers and dealerships. If I have 70.000 customers and 82 dealerships in 4 different chains it would be a massive calculation. I would have to calculate each customer vs the nearest dealership of each chain.
Or am I misinterpreting the use of 'calculating distance'?