Option Explicit

Private Sub Document_ContentControlOnExit(ByVal ContentControl As ContentControl, Cancel As Boolean)
    If ContentControl.Title = "Issue Date" Then
        If Not ContentControl.Range.Text = ContentControl.PlaceholderText Then
            ActiveDocument.SelectContentControlsByTitle("Expiry Date").Item(1).Range.Text = _
            DateAdd("m", 12, CDate(ContentControl.Range.Text))
        End If
    End If
End Sub