(Actually, with this method it's not necessary to have the first and third lines at all. Clipboard.AsText := Memo1.Text is all that's needed.)
procedure TForm1.Button1Click(Sender: TObject);begin Memo1.SelStart:=5; Memo1.SelLength:=10; Application.ProcessMessages; Clipboard.AsText:=Memo1.SelText; Memo1.SelLength := 0;end;