int cancel=false;
bool copyok=CopyFileEx(sFromPath,// name of existing file
sToPath,// name of new file
MyCopyProgressRoutine,// callback function
progressBar,// callback parameter
&cancel,// cancel status
NULL);// copy options

DWORD CALLBACK MyCopyProgressRoutine( 
LARGE_INTEGER TotalFileSize, // total file size, in bytes 
LARGE_INTEGER TotalBytesTransferred, // total number of bytes transferred 
LARGE_INTEGER StreamSize, // total number of bytes for this stream 
LARGE_INTEGER StreamBytesTransferred, // total number of bytes transferred for this stream 
DWORD dwStreamNumber, // the current stream 
DWORD dwCallbackReason, // reason for callback 
HANDLE hSourceFile, // handle to the source file 
HANDLE hDestinationFile, // handle to the destination file 
LPVOID lpData // passed by CopyFileEx 
)
{
QProgressBar *ukaz = (QProgressBar *) lpData;
double TBT=TotalBytesTransferred.QuadPart;
double TFS=TotalFileSize.QuadPart;
double delen=TBT/TFS*100;
ukaz->setProgress((int)delen);
return PROGRESS_CONTINUE; 
}

class MyThread : public QThread
{
public:
virtual void run();
};

void MyThread::run()
{
int cancel=false;
bool copyok=CopyFileEx(...);
}