Problem in editing security group of a file

 Hi all,

I am not able to edit   security group of a file.

following is the code i am using for changing meta data of a file

                binder.putLocal("IdcService", "FLD_EDIT_FILE");

                binder.putLocal("fFileGUID",fileid);

                binder.putLocal("dSecurityGroup","IJM_SHARED");

                // Write the data binder for the request to stdout

                 serializer.serializeBinder (System.out, binder);

                // Send the request to Content Server

                 ServiceResponse response1 = idcClient.sendRequest(userContext,binder);

                // Get the data binder for the response from Content Server

                DataBinder responseData1 = response1.getResponseAsBinder();

                // Write the response data binder to stdout

               serializer.serializeBinder (System.out, responseData1);

Please help on this 

Regards,

Shakir