uses
  ClipBrd;

procedure TForm1.Memo1KeyDown(Sender: TObject; var Key: Word;
Shift: TShiftState);
begin
  if ((Key = ord('V')) and (ssCtrl in Shift)) then
  begin
    if Clipboard.HasFormat(CF_TEXT) then
      ClipBoard.Clear;
    Memo1.SelText := 'Delphi World is COOL!';
    key := 0;
  end;
end;