I can't image how it is working as there is no such method in the Word Object model named "BookChange"
Code:
Sub ScratchMacro()
'A basic Word Macro coded by Gregory K. Maxey
Dim oRng As Range
Set oRng = ActiveDocument.Bookmarks("DatePP").Range
oRng.Text = Format(Now, "MMMM dd, yyyy")
ActiveDocument.Bookmarks.Add "DatePP", oRng
lbl_Exit:
Exit Sub
End Sub