文件复制程序，调试时无法通过，请高手指导。

下面的文件复制程序，调试时提示红字符无法通过，请高手看一看，到底错在什么地方？
procedure CopyFile(const FileName, DestName: TFileName);

var

CopyBuffer: Pointer;

TimeStamp, BytesCopied: Longint;

Source, Dest: Integer;

Destination: TFileName;

const

ChunkSize: Longint = 8192;

begin

Destination := ExpandFileName(DestName);

if HasAttr(Destination, faDirectory) then

Destination := Destination + '\' + ExtractFileName(FileName);

TimeStamp := FileAge(FileName);

GetMem(CopyBuffer, ChunkSize);

try

Source := FileOpen(FileName, fmShareDenyWrite);

if Source < 0 then

raise EFOpenError.Create(FmtLoadStr(SFOpenError, [FileName]));

try

Dest := FileCreate(Destination);

if Dest < 0 then

raise EFCreateError.Create(FmtLoadStr(SFCreateError,[Destination]));

try

repeat

BytesCopied := FileRead(Source, CopyBuffer^, ChunkSize);

if BytesCopied > 0 then

FileWrite(Dest, CopyBuffer^, BytesCopied);

until BytesCopied < ChunkSize;

finally

FileSetDate(Dest,TimeStamp);

FileClose(Dest);

end;

finally

FileClose(Source);

end;

finally

FreeMem(CopyBuffer, ChunkSize);

end;

end;

[此贴子已经被作者于2015-12-15 21:00编辑过]