The Visual FoxPro documentation states:

"For example, you might create a rule that compares the entry in the postal_code field of a table against a lookup table that contains the postal abbreviation codes for your country, and rejects any value that is not already present as a valid postal code abbreviation."

I am try to accomplish a task similar to the postal abbreviation code validation. Could someone tell me what I need in my Field Validation Rule? An example based on the postal abbreviation code would be wonderful. Thank You.