diff --git a/EXE.h b/EXE.h
index 6f45f0e..1a0b80c 100644
--- a/EXE.h
+++ b/EXE.h
@@ -16,6 +16,9 @@
 #include "GseContext.h"
 #include "/EgtDev/Include/EgtILogger.h"
 
+//-----------------------------------------------------------------------------
+HWND ExeGetMainWindowHandle( void) ;
+
 //----------------------------------------------------------------------------
 const std::string& ExeGetIniFile( void) ;
 
diff --git a/EXE_General.cpp b/EXE_General.cpp
index 7a167af..d82c979 100644
--- a/EXE_General.cpp
+++ b/EXE_General.cpp
@@ -44,6 +44,7 @@ static int     s_nKeyType = KEY_LOCK_TYPE_ANY ;
 static string  s_sIniFile ;
 static pfProcEvents s_pFunProcEvents = nullptr ;
 static pfOutText    s_pFunOutText = nullptr ;
+static HWND s_hMainWnd = nullptr ;
 
 //-----------------------------------------------------------------------------
 bool
@@ -427,6 +428,22 @@ ExeOutText( const string& sText)
       return false ;
 }
 
+//-----------------------------------------------------------------------------
+bool
+ExeSetMainWindowHandle( HWND hMainWnd)
+{
+   s_hMainWnd = hMainWnd ;
+   return true ;
+}
+
+//-----------------------------------------------------------------------------
+//-----------------------------------------------------------------------------
+HWND
+ExeGetMainWindowHandle( void)
+{
+   return s_hMainWnd ;
+}
+
 //-----------------------------------------------------------------------------
 //-----------------------------------------------------------------------------
 const string&
diff --git a/EgtExecutor.rc b/EgtExecutor.rc
index 4599336..87fcb21 100644
Binary files a/EgtExecutor.rc and b/EgtExecutor.rc differ
diff --git a/GenTools.cpp b/GenTools.cpp
index 9046844..91fbf7f 100644
--- a/GenTools.cpp
+++ b/GenTools.cpp
@@ -27,14 +27,15 @@ FindTopWindow( void)
    pair<HWND, DWORD> params = { 0, pid} ;
 
   // Enumerate the windows using a lambda to process each window
+   SetLastError( 0) ;
    BOOL bResult = EnumWindows( []( HWND hWnd, LPARAM lParam) -> BOOL 
                      {
                         auto pParams = ( pair<HWND, DWORD>*)(lParam) ;
 
                         DWORD processId ;
-                        if ( GetWindowThreadProcessId( hWnd, &processId)  &&
+                        if ( GetWindowThreadProcessId( hWnd, &processId) != NULL  &&
                              processId == pParams->second  &&
-                             GetWindow( hWnd, GW_OWNER) == (HWND) nullptr  &&
+                             GetWindow( hWnd, GW_OWNER) == NULL  &&
                              IsWindowVisible( hWnd)) {
                            // Stop enumerating
                            SetLastError( -1) ;
diff --git a/LUA_General.cpp b/LUA_General.cpp
index c19395a..b1923a0 100644
--- a/LUA_General.cpp
+++ b/LUA_General.cpp
@@ -242,7 +242,8 @@ LuaOutBox( lua_State* L)
    LuaGetParam( L, 4, bModal) ;
    LuaClearStack( L) ;
   // emetto la finestra di dialogo
-   int nRes = MessageBox( FindTopWindow(), stringtoW( sOut), stringtoW( sTitle),
+   HWND hTopWnd = ExeGetMainWindowHandle() ; // FindTopWindow() ;
+   int nRes = MessageBox( hTopWnd, stringtoW( sOut), stringtoW( sTitle),
                           MB_OKCANCEL | nIcon | ( bModal ? MB_TASKMODAL : MB_SYSTEMMODAL)) ;
   // risultato (Ok->true, Cancel->false)
    LuaSetParam( L, ( nRes == IDOK)) ;
@@ -304,7 +305,7 @@ LuaFileDialog( lua_State* L)
    OPENFILENAME ofn ;
    ZeroMemory( &ofn, sizeof( ofn)) ;
    ofn.lStructSize  = sizeof( ofn) ;
-   ofn.hwndOwner    = FindTopWindow() ;
+   ofn.hwndOwner    = ExeGetMainWindowHandle() ; // FindTopWindow() ;
    ofn.lpstrFilter  = LPWSTR( wsFilter) ;
    ofn.lpstrFile    = LPWSTR( wsFileName) ;
    ofn.nMaxFile     = MAX_PATH ;
@@ -622,7 +623,8 @@ LuaDialogBox( lua_State* L)
    }
    LuaClearStack( L) ;
   // lancio dialogo
-   bool bOk = ( DialogBox( GetModuleIstance(), MAKEINTRESOURCE( IDD_LUADLG), FindTopWindow(), (DLGPROC)DialogBoxProc) == IDOK) ;
+   HWND hTopWnd = ExeGetMainWindowHandle() ;  // FindTopWindow() ;
+   bool bOk = ( DialogBox( GetModuleIstance(), MAKEINTRESOURCE( IDD_LUADLG), hTopWnd, (DLGPROC)DialogBoxProc) == IDOK) ;
   // restituzione parametri
    if ( bOk) {
       STRVECTOR vRes ;