If you want to copy some lines of data from a Grid (Ctrl+C) and paste (Ctrl+V) it into an Excel document, just use following code:

procedure MyForm.Button1Click(Sender: TObject);
var
  i, j: integer;
  lString: string;
begin
  lString := '';
  for i := 0 to Grid.RowCount - 1 do begin
    for j := 0 to Grid.ColCount - 1 do begin
      lString := lString + Grid.Cells[j, i];
      if j < Grid.ColCount - 1 then 
        lString := lString + #9;
    end;
    if i < Grid.RowCount - 1 then 
      lString := lString + #13;
  end;
  Clipboard.AsText := lString;
end;

With few modifications this code can be also applied to TDrawGridEx.