[dr. F.I.N.]

я бы сделал примерно так:

Код:

procedure ConFontStyle(Bold, Italic, Underline, StrikeOut: Boolean; OBJ: TObject);
const
  FS: array [1..4, Boolean] of TFontStyles = (([],[fsBold]),
                                              ([],[fsItalic]),
                                              ([],[fsUnderLine]),
                                              ([],[fsStrikeOut]));
begin
 (OBJ as TMemo).Font.Style:= FS[1, Bold] +
                             FS[2, Italic] +
                             FS[3, Underline] +
                             FS[4, StrikeOut];
end;