I know how to add the Google Map on my restaurant's webpage, but how can I have range of delivery (semi-transparent polygon)?

Here is an example: [link](http://maps.google.com/maps/ms?ie=UTF8&oe=UTF8&msa=0&msid=205169863221025505100.0004b0255c8e6365a67df)

Maybe it can be done by somehow put a semi-transparent image on Google Map? But how can this be done?