Search within connected objects

For example I have two objects.

1. countries

2. cities

Each country has many cities. Every city is connected to one country.


Lets say I have following records:

Germany: Berlin, Hamburg

China: Hong Kong, Shanghai


When I add a search field for country and one for city the two search fields are not dependent.

I can choose Germany and Hong Kong.


How can I set it up whenever I choose for example China that I only can choose Chinese cities?

I know when I add an Add Form it works. But the search just doesn't work.


Hope anyone understood what Im talking about




can you provide a script for that? I'm not really familiar with JavaScript. Or do you have a example how I can achieve that functionality.


Thanks in advance


This can be achieve using some custom JavaScript. In Knack there is no such functionality. 

You only want to minimise the values in city field after selecting country 


Sunny Singla