How To Use Contextual Filters With OG Vocabulary?

Hi
I have two content types groups
for example

Content Type One: News & City
Content Type Two: Events & City

Main content is News & City
If there news in city = Vocabulary term "New York"

The block in the sidebar Contextual Filters
will show show all events = "New York" Vocabulary term

Do you know how to do this please?
Many Thanks for your time and help