SOLUTION
Private Declare Function FindWindowA Lib "USER32" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function GetWindowLongA Lib "USER32" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetWindowLongA Lib "USER32" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Sub Workbook_Open()
Dim hwnd As Long
hwnd = FindWindowA(vbNullString, Application.Caption)
SetWindowLongA hwnd, -16, GetWindowLongA(hwnd, -16) And &HFFF7FFFF
End Sub
Private Sub Workbook_BeforeClose(Cancel As Boolean)
Dim hwnd As Long
hwnd = FindWindowA(vbNullString, Application.Caption)
SetWindowLongA hwnd, -16, GetWindowLongA(hwnd, -16) Or &H80000
End Sub