I believe this code will fail. Maybe in 2007 it works, but it certainly does
not work for earlier versions. The .Name property of Bookmarks is read-only.
You can not change the names of bookmarks. You must use the range of the
bookmark and make a new bookmark (giving the new bookmark the name you want).
You also have to be careful about deleting the old bookmark names because of
the way Word deals with the bookmark collection. It is best to do your
creation of new bookmarks, THEN delete the old ones with something like:
Sub ChangeBM()
Dim oBk As Bookmark
Dim oBM_Delete()
Dim j As Long
Dim var
For Each oBk In ActiveDocument.Bookmarks
' make a new bookmark using SAME range
ActiveDocument.Bookmarks.Add _
Name:="Test_" & oBk.Name, _
Range:=oBk.Range
' add the old name to an array
ReDim Preserve oBM_Delete(j)
oBM_Delete(j) = oBk.Name
j = j + 1
Next oBk
' now delete the old bookmarks
For var = 0 To UBound(oBM_Delete())
ActiveDocument.Bookmarks(oBM_Delete(var)).Delete
' note this deletes the bookmark
' NOT the range
Next
End Sub