How to trace close event of a document & stop that functionality..

Hi,

    Im new to Indesign SDK.  I need to open a document and do some changes in that.  When i closing that document i have to capture that event and just have to give one alert message which i did (Ex. close) and have to stop  that functionality(Close). 

     I can trace the event through Signal Manager of ServiceID  but dont know How to stop that close function?  When entering this cases

          case kBeforeCloseDocSignalResponderService:
        {
            DocWchUtils::DwAlert(doc, kBeforeCloseDocSignalStringKey);
            break;
        }
        case kAfterCloseDocSignalResponderService:
        {
            DocWchUtils::DwAlert(doc, kAfterCloseDocSignalStringKey);
            break;
        }

     Its gives alert and also file closed.  How can i stop that file closing?

     Pls someone help me?