Disabling a UserForm's Close Button

Activate the code module for your UserForm, and enter the following procedure:

Private Sub UserForm_QueryClose _
  (Cancel As Integer, CloseMode As Integer)
'   Prevents use of the Close button
    If CloseMode = vbFormControlMenu Then
        MsgBox "Clicking the Close button does not work."
        Cancel = True
    End If
End Sub

When the user clicks the Close button, a message box appears and the UserForm remains open.