How to display unique Error message for when they are part of groups

How to display unique Error message for when they are part of groups

I am new in jQuery. Need to validate a form. I am trying to validate a USA address. I have attached a screenshot for that. Basically I have to display common error message like "Please enter a city & state" when both city and state are missing and user click on submit button.  And when user enters city, it should display "Please enter state". Alternatively when user enters state, it should display "Please enter state". I tried the "groups" functionality to display a common error message. But not able to display unique error message when either city or state missing. 

I tried like that

groups: {
      cityState : "city state"
}

and put common message "Please enter a city & state" in message area. not able to understand how to display unique error message for each field. Tried by adding additional methods but did not work.

Any help will be highly appreciated.

Thanks
Amit