Fórum Ajuda com InputBox #425305

Const
  InputBoxMsg = WM_USER + 123;

  private
    { Private declarations }
    procedure InputBoxSet(var Msg: TMessage); message InputBoxMsg;

procedure TForm1.InputBoxSet(var Msg: TMessage);
var
  i: integer;
begin
  for i:=0 to Screen.Forms[0].ComponentCount-1 do
  begin
    if Screen.Forms[0].Components[i] is TEdit then
    begin
      With TEdit( Screen.Forms[0].Components[i] ) do
      begin
        PasswordChar := '*'; 
        Clear;                
      end;
    end;
  end;
end; 

var
  Senha: string;
begin

  PostMessage(Handle, InputBoxMsg, 0, 0);
  Senha := InputBox('Autenticação', 'Informe sua senha:', '');
  if Senha <> '' then
    ShowMessage('A senha informada foi: ' + Senha);
end;

Contruindo a procedure que fará a transformção:

#Código
procedure TForm1.InputBoxSet(var Msg: TMessage);
var
i: integer;
begin
for i:=0 to Screen.Forms[0].ComponentCount-1 do
begin
if Screen.Forms[0].Components[i] is TEdit then
begin
With TEdit( Screen.Forms[0].Components[i] ) do
begin
PasswordChar := '*';
Clear;
end;
end;
end;
end;

var
  hInputForm, hEdit: HWND;
begin
  hInputForm := Screen.Forms[0].Handle;
  if (hInputForm <> 0) then
  begin
    hEdit := FindWindowEx(hInputForm, 0, 'TEdit', nil);
    SendMessage(hEdit, EM_SETPASSWORDCHAR, Ord('*'), 0);
  end;

end;