Private Sub CheckBox1_Click()
  If CheckBox1.Value = True Then
    Call UpdateBookmark("Destination", "ATEntry" & vbCr)
  Else
    Call UpdateBookmark("Destination")
  End If
End Sub
 Sub UpdateBookmark(BmkNm As String, Optional strATName As String)
Dim BmkRng As Range
With ActiveDocument
  If .Bookmarks.Exists(BmkNm) Then
    Set BmkRng = .Bookmarks(BmkNm).Range
    If strATName <> vbNullString Then
       Set BmkRng = ActiveDocument.AttachedTemplate.AutoTextEntries(strATName).Insert(Where:=BmkRng)
    Else
      BmkRng.Text = vbNullString
    End If
    .Bookmarks.Add BmkNm, BmkRng
  End If
End With
Set BmkRng = Nothing
End Sub