CountryBoy1 asks "Why won't the validation work while editing is performed on the given record ?" Record validation won't take place until the record is "committed". This happens when you exit the record in some manner such as when you click or tab to the next record. Until then, Filemaker assumes that you are still entering or modifying data and won't check validation until you are "finished". Exiting the record is the signal (trigger) to filemaker to do that.
If you are using FMP 10, you can set script triggers to check values when a field is exited, when it is modified or even when a specific key is pressed. I use script triggers with one of these events to check for errors before the record is commited. If you use v10, that's your best choice.
Thanks for your reply. I sort of figured it was necessary to exit the record,
but was hoping for another answer. I am using Filemaker Pro 9. Doubt if
I will go to Version 10 anytime soon.
I have selected your reply as the answer to my question.