Solidworks Addin: PMPHandler won't raise OnClose event

I have a SolidWorks addin that use a Property Manager Page.  I need to detect when it is no longer displayed.

Intuitively, this would be captured by the OnClose sub function in PMPHandler.vb

     Sub OnClose(ByVal reason As Integer) Implements PropertyManagerPage2Handler8.OnClose
        ''This function must contain code, even if it does nothing, to prevent the
        ''.NET runtime environment from doing garbage collection at the wrong time.

        iThisModDoc = Nothing 'Get rid of the iSWAsyDoc from the main class (stop listening for this)

     End Sub

This event is raised if the user cancels the PMP with "X" or "Check", but not if the user hits Escape or Cntr-Q, etc. The PMP disapears, but not event is fired and I cannot detect the that PMP is no longer visible to the user.

Any ideas?

SolidworksApi macros