请问高手插件主程序中能不能得到插件程序窗体关闭时的消息？？？

本人在工作中创建一个插件窗体，编译成Dll文件，然后通过插件主程序调用：插件Dll应放在和插件主程序下的plugins目录下；当时我创建的是模式窗体，可是后来我想创建一个无模式窗体。请问高手我能不能在插件主程序中得到插件窗体关闭时的消息？（或者是说我能不能控制只创建一个无模式窗体？），如有高手指教，在下将感激不仅。
---------------------------------------------插件窗体-------------------------------------------------------------------------------library Plugins;uses
  SysUtils,
  Classes,
  PlugFrm in 'PlugFrm.pas' {frmPlugins};
exports
  ShowDllForm,GetCaption;
{$R *.res}begin
end.------------------------------------------------------------------------------------------------------------------------
unit PlugFrm;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, CheckLst, Grids, Mask, Buttons;type
  TfrmPlugins = class(TForm)
    BitBtn1: TBitBtn;
    DrawGrid1: TDrawGrid;
    CheckListBox1: TCheckListBox;
  private    { Private declarations }
  public
    { Public declarations }
  end;
var
  frmPlugins: TfrmPlugins;
  function ShowDllForm(AHandle:THandle;ACaption:string):integer;stdcall;
  function GetCaption:pChar;stdcall;
implementation{$R *.dfm}function GetCaption:pchar;stdCall;
begin
  Result:='插件程序测试窗体';
end;function ShowDllForm(AHandle:THandle;ACaption:string):integer;stdcall;
var
  Dll_Form:TFrmPlugins;
begin
  Result:=0;
  try
    Application.Handle:=AHandle;
    //if not assigned(Dll_Form) then //是否已建立实例
      Dll_Form:=TFrmPlugins.Create(Application);
    try
      Dll_form.Caption:=ACaption;
      //Dll_form.ShowModal
      Dll_form.Show;
    finally
      //Dll_form.Free;
    end;
  except
    Result:=1;
  end;
end;
end.-------------------------------------------------插件主程序-----------------------------------------------------------------------
unit PluginMain;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, Menus, StdCtrls;type
  TForm1 = class(TForm)
    MainMenu: TMainMenu;
    fds1: TMenuItem;
    fdas1: TMenuItem;
    N_plugins: TMenuItem;
    ListBox1: TListBox;
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    procedure LoadPlugins;
    procedure PlugInsClick(Sender:Tobject);
    procedure FreePlugIns;
    procedure SearchFileExt(Const Dir,Ext:String;Files:TStrings);
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}type
  TShowDllForm = function(AHandle:THandle;ACaption:string):integer;stdcall;  TGetCaption = function:Pchar;Stdcall;  EDllLoadError = Class(Exception);  TTestPlugin = class
    Caption:String;
    Address:THandle;
    Call:Pointer;
  end;var
  plugins:TList;{ TForm1 }procedure TForm1.SearchFileExt(Const Dir,Ext:String;Files:TStrings);
var
  Found:TSearchRec;
  Finished:integer;
begin
  Finished:=findfirst(Dir+'*.*',faAnyFile ,Found);
  while (Finished=0)  do
  begin
    if pos(uppercase(ext),uppercase(Found.Name))>0 then
      Files.Add(Dir+Found.Name);
    finished:=findNext(Found);
  end;
  FindClose(Found);
end;procedure TForm1.LoadPlugIns;
var
  Files:TStrings;
  i:integer;
  TestPlugIn:TTestPlugin;
  NewMenu:TmenuItem;
  GetCaption:TGetCaption;
  s:string;
begin
  Files:=TStringlist.Create;//文件列表
  Plugins:=TList.Create;//插件列表  s:=ExtractFilePath(Application.ExeName)+'Plugins\';  SearchFileExt(s,'.dll',Files);
  for i:=0 to files.Count-1 do
  begin
    TestPlugIn:=TTestPlugin.Create;
    TestPlugIn.Address:=LoadLibrary(Pchar(Files[i]));
    if TestPlugIn.Address=0 then
      Raise EDllLoadError.Create('装载'+Pchar(Files[i])+'失败');
    try
      @GetCaption:=GetProcAddress(TestPlugin.Address,'GetCaption'); //取函数地址
      TestPlugIn.Caption:=Getcaption;
      TestPlugIn.Call:=GetProcAddress(TestPlugin.Address,'ShowDllForm'); //取函数地址      PlugIns.Add(TestPlugIn);//加插件列表      Newmenu:=TMenuItem.Create(self);
      NewMenu.Caption:=TestPlugIn.Caption;
      NewMenu.OnClick:=PlugInsClick;
      NewMenu.Tag:=i;//插件标识
      N_PlugIns.Add(Newmenu);  //加插件表单
    except
      raise EdllLoadError.Create('初始化失败');
    end;
  end;
end;procedure TForm1.freePlugins;
var i:integer;
begin
  for i:=0 to PlugIns.Count-1 do
  begin
    FreeLibrary(TTestPlugIn(PlugIns[i]).Address);//释放插件实例
  end;
  PlugIns.Free;//释放插件列表
end;procedure TForm1.PlugInsClick(Sender: Tobject);
var
  ShowDllForm:TShowDllForm;
begin
  //取插件函数地址
  @ShowDllForm:=TTestplugin(PlugIns[TMenuItem(Sender).Tag]).Call;
  //通过插件表示调用插件函数
  if ShowDllForm(Application.Handle,TTestPlugin(PlugIns[TmenuItem(sender).Tag]).Caption)=1 then
    ShowMessage('打开窗体错误');
end;procedure TForm1.FormCreate(Sender: TObject);
begin
  LoadPlugIns;
end;procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  FreeplugIns;
end;end.