[ecfisa]

Hola.

Yo la modificaría un poco,

Código Delphi [-]
procedure ShowFormIn(frmClass: TFormClass; Container: TWinControl);
var
  i : Integer;
begin
  for i := Screen.FormCount-1 downto 0 do
  if Screen.Forms[i] is frmClass then
  begin
    Screen.Forms[i].BringToFront;
    Exit;
  end;
  with frmClass.Create(Application) do
  begin
    Parent   := Container;
    Align    := alClient;
    Position := poMainFormCenter;
    Show;
  end;
end;

De ese modo te permitirá usar diferentes contenedores, por ejemplo:

Código Delphi [-]
begin
  ShowFormIn(TForm2, Memo1);
  ShowFormIn(TForm3, Edit1);
  ShowFormIn(TForm4, Panel1);
  ShowFormIn(TForm5, ListBox1);
end;

Saludos