Couldn't you get the various size values during the Load event i.e.

Private Sub MDIForm_Load()

MDIHeight = me.height
MDIWidth = me.width

End Sub

And then in the resize event, reassign these values so when the user resizes the form it goes back the way it was, i.e.

Private Sub MDIForm_Resize()

Me.Width = MDIHeight
Me.Height = MDIWidth

End Sub