Event register problem

hi,

i am new in adobe bridge.

when i select a thumbnail or file in content that time i want to $.writeln("someting");

for this i register e event but that is not working please help me in this regards. i'm working on adobe bridge cs5

i'm writing this code in  SnpListenDocEvents.jsx file.

onThumbnailEvent = function( event ){

          if( event.object .constructor.name == "Thumbnail" ){  // also use if( event.object instanceof Thumbnail ){

                    if( event.type == "select" ) {

                              $.writeln("your code is here");

                              return {handled:true};//stop processing event handlers

                    }

          }

}

// register the handler

allDocEventHandlers = { handler: onThumbnailEvent };

app.eventHandlers.push( allDocEventHandlers );