Create macro that updates fields before save - vba

Question

I'm new to VBA and am trying to write a macro that will execute a field update before the user saves the document. My first attempt was going to be intercepting the Save command like this:
Sub FileSave()
'
' FileSave Macro
' Saves the active document or template, and updates fields
'
Fields.Update
ActiveDocument.Save
End Sub
But one guide recommended not doing that and instead using DocumentBeforeSave(), so this is my new attempt:
Private Sub oApp_DocumentBeforeSave(ByVal Doc As Document, _
SaveAsUI As Boolean, Cancel As Boolean)
Fields.Update
End Sub
The first example gives me the following error:
"Runtime error '424': Object required"
The second example doesn't update the fields. I've tried the second code in both the ThisDocument object, and as a new module class. Nevertheless, the fields are still not updating when I save. On a side note, they work with this.
Private Sub Document_Close()
Fields.Update
Save
End Sub
It seems like a simple task but it just doesn't seem to work.

Answer 1

In your ThisDocument code module, add an Application object using the WithEvents keyword so that you can respond to its events:
Dim WithEvents TheApp As Word.Application
Add an event handler for Document_Open() that assigns your variable to the active Application object:
Private Sub Document_Open()
Set TheApp = ThisDocument.Application
End Sub
Add an event handler for Application_DocumentBeforeSave(). Within this event use the Doc object that's passed to it to update your document:
Private Sub TheApp_DocumentBeforeSave(ByVal Doc As Document, SaveAsUI As Boolean, Cancel As Boolean)
Doc.Fields.Update
End Sub
Save your document as a "Macro-Enabled Document (*.docm)".
Close the document and reopen it.
That should be it. If you want to make sure your code is working properly, add a breakpoint or a MsgBox() before your Doc.Fields.Update statement to make sure the event handler is getting called and check your values before and after the update.