Here is the script. The code is below.
///////////////////////////////////////////////////////////////////////////////////////////////
var googleMaps = {
  description: "Get directions on Google Maps",
  shortDescription: "Map direction",
  scope: {
    semantic: {
			"hCalendar" : "location"
    }
  },
  doAction: function(semanticObject, semanticObjectType) {
    if (semanticObjectType == "hCalendar") {
			var lookup_from = prompt("Directions to "+semanticObject.location+" from?","168-173, High Holborn, London");
			return "http://maps.google.com/maps?saddr="+lookup_from+"&daddr="+semanticObject.location;
    }
  }//do action
};

SemanticActions.add("googleMaps", googleMaps);
///////////////////////////////////////////////////////////////////////////////////////////////////