Visio Guy

I don't see any documentation on this, so maybe I'm doing something wrong.  I'm trying to use the "User-defined Cells" section of the document's shapesheet to store some persistent values.    I know how to access the shapesheet for shapes and pages, but I'm not having any luck with the document shapesheet (is it read only?).  Any suggestions on VBA I can use in a userform to read / write to those cells?  Or are there better ways to store persistent global variables?

To access the document sheet user cells, 'TheDoc!User.yourcell'

the doc sheet for documents (and pages) can be accessed the same way as shapes

    Dim docSheet As Visio.Shape
    Dim visDoc As Visio.Document
    Set visDoc = Application.ActiveDocument
    Set docSheet = visDoc.DocumentSheet
    ' do something with the document sheet

    Dim pagSheet As Visio.Shape
    Dim visPage As Visio.Page
    Set visPage = Application.ActivePage
    Set pagSheet = visPage.PageSheet
    ' do something with the page sheet

al