Как обратиться к переменной MDIChild

unit NewForm;
interface
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ComCtrls, StdCtrls, ExtCtrls;
type
  TNForm = class(TForm)
    .....
  private
    { Private declarations }
  public
    { Public declarations }
     inf: shotstring;
  end;
 
var
  NForm: TNForm; 
 
implementation
 
uses Main, PrivateForm;
 
{$R *.dfm}
 
.....
 
end.

procedure TMain1.CreateForm(Cap, Name: String);
var
   i: word;
begin
     for i:= 0 to Main1.MDIChildCount - 1 do
     begin
          if (Main1.MDIChildren[i].inf = Cap) and (Main1.MDIChildren[i].Tag = 2) then exit;
     end;
     NForm:= TNForm.Create(Main1);
     NForm.Name:= Name + IntToStr(Main1.MDIChildCount);
     NForm.Caption:= Cap;
     NForm.Inf:=Cap;
     NForm.Tag:=2;
....
     NForm.Say.SetFocus;
end;

if (Main1.MDIChildren[i] is TNForm) and (TNForm(Main1.MDIChildren[i]).inf = Cap)

TNForm(Main1.MDIChildren[i]).inf = Cap

property MDIChildren[I: Integer]: TForm;

TNForm(Main1.MDIChildren[i])