Simpler and more comprehensive:
Code:
Sub AutoNew()
Dim TOC As TableOfContents
For Each TOC In ActiveDocument.TablesOfContents
TOC.Update
Next
End Sub
Note that the above fully updates the TOC (e.g. for new/edited entries), whereas Charles' version only updates the page #s (though I don't know why anything about a TOC would need updating via an AutoNew macro - AutoOpen I could understand).