Variant(WordApplication1.ActiveDocument).foo()

procedure TForm1.Button4Click(Sender: TObject);
var
  LCID :integer;
  DispID1 : Integer;
  exInf :TExcepInfo;
  erPar :UINT;
  parArray :array of Variant;
  aDispId     :  TDispId;
  s :WideString;
  params :TDispParams;
  opResult: HResult;
  XlsIDispatch: IDispatch;
  WorkBooksIDispatch: IDispatch;
  VarRes: OleVariant;
begin
  XlsIDispatch := xls; {xls := CreateOleObject('Excel.Application');}
  LCID := GetUserDefaultLCID;

  s := 'Visible';
  opResult := XlsIDispatch.GetIDsOfNames(GUID_NULL, @s, 1, LCID, @DispID1);

  parArray := VarArrayCreate([0,0], varBoolean);
  parArray[0] := True;
  aDispId := DISPID_PROPERTYPUT;

  params.cArgs := length(parArray);
  params.rgvarg := @parArray[0];
  params.cNamedArgs := 1;
  params.rgdispidNamedArgs := @aDispId;

  opResult := XlsIDispatch.Invoke(DispID1, GUID_NULL, LCID, DISPATCH_PROPERTYPUT, params, @VarRes, @exInf, @erPar);


  s := 'WorkBooks';
  opResult := XlsIDispatch.GetIDsOfNames(GUID_NULL, @s, 1, LCID, @DispID1);
  params.cArgs := 0;
  params.rgvarg := nil;
  params.cNamedArgs := 0;
  params.rgdispidNamedArgs := nil;
  opResult := XlsIDispatch.Invoke(DispID1, GUID_NULL, LCID, DISPATCH_PROPERTYGET, params, @VarRes, @exInf, @erPar);

  WorkBooksIDispatch := VarRes;

  s := 'Add';
  opResult := WorkBooksIDispatch.GetIDsOfNames(GUID_NULL, @s, 1, LCID, @DispID1);
  opResult := WorkBooksIDispatch.Invoke(DispID1, GUID_NULL, LCID, DISPATCH_PROPERTYGET, params, @VarRes, @exInf, @erPar);
  VarRes := UnAssigned;

end;