Office 64 Bit code compatibility

I have an add-in that works in Word 32 bit but I'm having compatibility issue with Word 64 bit and I don't have a platform to test it with.  I've used the MS code compatibility checker, and made the changes suggested by it, but a remote user states that it still won't work.  The problem (at least one problem) appears to be in a code module that is used to "hide" the "X" button in a userform title bar.

I'm hoping that someone with Office 64 bit can evaluate/test this code to see if it works for them and if necessary correct so that it will work:

All you need is a new blank document and add a UserForm.  In a standard module named "FormControl" add this code:

Option Explicit
#If VBA7 Then
  Private Declare PtrSafe Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, _
        ByVal lpWindowName As String) As LongPtr
#Else
  Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
                                    (ByVal lpClassName As String, _
                                     ByVal lpWindowName As String) As Long
#End If
#If VBA7 Then
  Private Declare PtrSafe Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As LongPtr, _
                       ByVal nIndex As LongPtr) As LongPtr
#Else
  Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _
                                       (ByVal hwnd As Long, _
                                        ByVal nIndex As Long) As Long
#End If
#If VBA7 Then
  Private Declare PtrSafe Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
                                         (ByVal hwnd As LongPtr, _
                                          ByVal nIndex As LongPtr, _
                                          ByVal dwNewLong As LongPtr) As LongPtr
#Else
  Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
                                       (ByVal hwnd As Long, _
                                        ByVal nIndex As Long, _
                                        ByVal dwNewLong As Long) As Long
#End If
Const WS_SYSMENU = &H80000
Const GWL_STYLE = (-16)

Sub HideCloseButton(oDialog As Object)
'Hides the close button on a userform
#If VBA7 Then
  Dim hwnd As LongPtr, lStyle As LongPtr
#Else
  Dim hwnd As Long, lStyle As Long
#End If
  'All userforms have class name "ThunderDFrame" unrelated to the form name.
  hwnd = FindWindow("ThunderDFrame", oDialog.Caption)
  lStyle = GetWindowLong(hwnd, GWL_STYLE)
  SetWindowLong hwnd, GWL_STYLE, lStyle And Not WS_SYSMENU
lbl_Exit:
  Exit Sub
End Sub

Add a command button to the userform and in the userform module add this code:

Private Sub UserForm_Activate()

  FormControl.HideCloseButton Me

End Sub

Private Sub commandbutton1_click()

  Unload Me

End Sub

Thanks.