There are two steps then for right implementation:
The easiest way to do this is to use the Location entity of the Google Maps module. You have to create a Location object, with as address attribute your zipcode
For the right marker to appear, you need to give the Google Maps widget a XPath constraint to the entity you are clicking on in your datagrid. In my application I have an AddressData entity which holds all the address information and is the source of my datagrid. My XPath constraint is:
[GoogleMaps.Location_AddressData/Register.AddressData/id = '[%CurrentObject%]']
Off course, this association 'Location_AddressData' needs to exist in your domain model.
Hope this helps!