How to resize Google maps Dynamically?

Hi,

I have one tree widget and one google map widget. Tree widget contains list of locations (lets say cities), when location/city is selected from tree widget it should be displayed at the center of map and map should shrink (the actual size of map) to some specified height and width and the location should be displayed at center.

      Fig (a)Fig (b)

Something as above. Is there any way to achieve this functionality? Please advise.

Thanks,

Omkar