how can I changes values of filter dynamically?

Hello I have implement search based on 3 dropdown.
1)Region
2)Province
3)City

So if i select a region then the other two filter should be filled based on the selected region.

I have implemented the code for filling the province dropdown based on region. But after selecting the province its refilling the province filed
to solve this issue i want toknow which filter is clicked - in the redercallback .