[NumLock]

Код:

type
  TSendStruct = record
...
  end;
var
  FMemoryStream: TMemoryStream;
  data: TSendStruct;
  dummy: Cardinal;
begin
  FMemoryStream:=TMemoryStream.Create;
  try
    FMemoryStream.Write(data, SizeOf(TSendStruct));
    FMemoryStream.Write(data, SizeOf(TSendStruct));
    FMemoryStream.Write(data, SizeOf(TSendStruct));
    FMemoryStream.Write(data, SizeOf(TSendStruct));
    WriteFile(h, FMemoryStream.Memory^, FMemoryStream.Size, dummy, nil);
  finally
    FMemoryStream.Free;
  end;
end;

WriteFile это к примеру!