Private Const GWL_STYLE = -16
Private Const WS_SYSMENU = &H80000
Private Const WS_MINIMIZEBOX = &H20000
Private Const WS_MAXIMIZEBOX = &H10000

Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _
    (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
    (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function GetParent Lib "user32" (ByVal hwnd As Long) As Long
 
Public Sub LockAppWindow(fForm As Form)
    ModifyAppWind fForm.hwnd
    MsgBox "Ciao ciao pulsantini!"
End Sub

Private Sub ModifyAppWind(wChildWnd)
    Dim wParentWnd As Long
    wParentWnd = GetParent(GetParent(wChildWnd))
    Dim PrevWinStyle As Long, NewWinStyle As Long
    PrevWinStyle = GetWindowLong(wParentWnd, GWL_STYLE)
    NewWinStyle = PrevWinStyle And Not WS_SYSMENU And _
       Not WS_MINIMIZEBOX And _
       Not WS_MAXIMIZEBOX
    PrevWinStyle = SetWindowLong(wParentWnd, GWL_STYLE, NewWinStyle)
End Sub