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Const
  CR = #13#10;

procedure TForm1.Button1Click(Sender: TObject);
Begin
  If Pos (
        CR + CR,
        Copy (RichEdit1.Lines.Text, RichEdit1.SelStart, Length (RichEdit1.Lines.Text))
      ) > 0
  Then
    RichEdit1.SelStart := RichEdit1.SelStart + Pos (
        CR + CR,
        Copy (RichEdit1.Lines.Text, RichEdit1.SelStart, Length (RichEdit1.Lines.Text))
      ) + Length (CR);

  RichEdit1.SetFocus;
end;