Neal,
Are you trying to validate messages at runtime, or validate the values entered into business rules at design time. In your scenario, the vocabulary would only limit the range of values that you could enter at design time. If you want runtime validation, here are some things you could try:
- Use a vocab that points at a C# helper that does the validation using constants defined in the code.
- Create a database lookup vocab that validates the message against values in a database table.
- Keep the constant vocab, and add a condition for each value in the list.
Hope this helps!