[atani123]

Me respondo

He creado un formulario del que heredan todos los forms.

Código Delphi [-]
unit Formulario;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
Tfrm = class(TForm)
private
{ Private declarations }
public
{ Public declarations }
end;
var
frm: Tfrm;
function MessageDlg(const Msg: string; DlgType: TMsgDlgType; Buttons: TMsgDlgButtons; HelpCtx: Longint): Word;
implementation
{$R *.dfm}
function MessageDlg(const Msg: string; DlgType: TMsgDlgType; Buttons: TMsgDlgButtons; HelpCtx: Longint): Word;
Var
newMsg : String;
Begin
newMsg := Uppercase( Msg);
Result := Dialogs.MessageDlg( newMsg, DlgType, Buttons, HelpCtx);
End;
end.

Por si a alguien le puede servir