Passing variable pointer as string to another function

With Delphi 7 I need to create a TStream variable and use/free it in another part of the code. Unfortunately it cannot be passed as "normal" parameter.

I created a simple application for testing what I need, using some examples I found on Google and some help from SOF (I am not used to pointers).

Here is what I got so far (it uses an Edit, a Memo e 3 Buttons):

function IsObject(Address: Pointer): Boolean; assembler;
asm
  MOV     EAX, [Address]
  CMP     EAX, EAX.vmtSelfPtr
  JNZ     @False
  MOV     Result, True
  JMP     @Exit
@False:
  MOV     Result, False
@Exit:
end;

procedure TForm1.btnSetMem1Click(Sender: TObject);
var
  Stm: TStream;
begin
  Stm := TMemoryStream.Create;
  edtMemID1.Text := IntToStr(Integer(Stm));
end;

procedure TForm1.btnSaveMem1Click(Sender: TObject);
var
  Stm: TStream;
begin
  Stm := Pointer(StrToInt(edtMemID1.Text));
  if IsObject(Stm) then
  try
    memStm1.Lines.SaveToStream(Stm);
    btnSaveMem1.Enabled := False;
    btnLoadMem1.Enabled := True;
    memStm1.Clear;
  except
    FreeAndNil(Stm);
  end;
end;

procedure TForm1.btnLoadMem1Click(Sender: TObject);
var
  Stm: TStream;
begin
  Stm := Pointer(StrToInt(edtMemID1.Text));
  if IsObject(Stm) then
  try
    Stm.Position := 0;
    memStm1.Lines.LoadFromStream(Stm);
  except
    FreeAndNil(Stm);
  end;
end;

procedure TForm1.btnFreeMem1Click(Sender: TObject);
var
  Stm: TStream;
begin
  Stm := Pointer(StrToInt(edtMemID1.Text));
  if IsObject(Stm) then FreeAndNil(Stm);
  btnSaveMem1.Enabled := False;
  btnLoadMem1.Enabled := False;
  edtMemID1.Clear;
end;

procedure TForm1.edtMemID1Change(Sender: TObject);
begin
  btnSaveMem1.Enabled := (Trim(edtMemID1.Text) <> '');
  btnFreeMem1.Enabled := (Trim(edtMemID1.Text) <> '');
end;

The ASM function I found here and seems to be working. I also tested with FastMM and there is no memory leak (if btnFreeMem is used).

Please review this code and maybe give some tips to make it better or avoid problems (memory leaks).