Return list based on if filtered

Place                Region

place 1                 A

place 2                 A

place 3                 B

place 4                 B

Hello, I need some help with a table such as the above. I have a slicer on region. If Region is not filtered, I want a list of Regions, but if it is filtered I want a list of Places for that region.

E.G

Filter :

ALL

Return:

Region A

Region B

Filter:

Region A

Return:

Place 1

Pleace 2

Thank you