想读取二进制文件指定位置如何实现啊

想读取二进制文件指定位置怎么实现啊？
我是菜鸟
大家　多帮助啊　　１


[解决办法]
//读取haha.txt文件第3字节开始4个字节的内容,haha.txt的内容为1234567
procedure TForm1.Button1Click(Sender: TObject);
var
hFile: THandle;
iBytesRead: Integer;
Buffer: PChar;
begin
try
hFile := FileOpen( 'C:\haha.txt ', fmOpenRead);
FileSeek(hFile,2,0);
GetMem(Buffer,5);
FileRead(hFile, Buffer^,4);
ShowMessage(Buffer);
finally
FileClose(hFile);
FreeMem(Buffer);
end;
end;