Having Visio update shape data automatically

Part of my job is to have an up to date documentation of all integrations we have. I am used to using Visio for this, and have at my previous clients kept it quite simple with manual formatting for visualizing if a message is under construction or to be deleted etc.

At this moment, I am trying out having "a lot" of documentation gathered in the Visio document. Besides having shapes for "Systems" and connections between these that each is equivalent of a "Message", I have added custom data fields on these that allow me to document metadata on each message flow. Part of the metadata I have on a message is Id, Name, Trigger, Status, Transport type and so on. Some of these fields are then used to dynamically alter the format of the connection to give a visual cue to the underlying data. If the Status is "Planned" I give the connection a green color, if the connection is marked as "Request/Response" I visualize this by having a symbol indicating so.

This all works fine and gives me one single document for the overview of the integrations. I then thought of implementing a change list so that I could follow up on revisions of the diagram. Having a normal text based change list on a separate sheet would be possible, but would incur manual work to update it and also not be mandatory (meaning that it would be forgotten and hence useless). Instead, I opted for an extra custom data field on the shapes used indicating the last time the shape was updated (data wise, not if it was moved). This is handled automatically by code that triggers when the shape data is updated.

I have one class module called "UpdateShapeTimeStamp":

Dim WithEvents appObj As Visio.Application

Private Sub appObj_CellChanged(ByVal Cell As IVCell)
    If (Cell.Shape.CellExists("Prop.Updated", 0)) Then
        Cell.Shape.CellsU("Prop.Updated").FormulaU = Chr(34) & Now() & Chr(34)
    End If
End Sub

Private Sub Class_Initialize()
    Set appObj = Application
End Sub

Private Sub Class_Terminate()
    Set appObj = Nothing
End Sub

and the Document code to enable this code:

Dim UpdateShapeTimeStampClass As UpdateShapeTimeStamp

Private Sub Document_BeforeDocumentClose(ByVal Doc As IVDocument)
    Set UpdateShapeTimeStampClass = Nothing
End Sub

Private Sub Document_DocumentOpened(ByVal Doc As IVDocument)
    Set UpdateShapeTimeStampClass = New UpdateShapeTimeStamp
End Sub

Now when changing the shape data on any shape, the event will trigger and check if the custom field "Updated" is available (meaning that it is one of my custom shapes) and if so, set it to the current datetime.

This allows me to have an automatic tracking of all changes in the diagram for each shape. Neat!