Show value on look up when we click another look up

Hello all,

I have a query , where i have two look up with the name city and service coordinator.

what i am looking for is : when i select city , then coordinator name is filtering on the look up ,but what i want is to show the name directly on the look up,without clicking on look up.

For e.g.:  when i select city delhi ,then name should auto populate on the look up without going through in the look up.