>>See FieldChanged function from the message link I gave you. (at the bottom of the message).
>
>I will check the function although I am very careful not to make too many changes in the existing code. You see, the existing code worked except for the case of the old value being logical and new value being NULL. Once I added reversed comparison the code works (so far in my tests).

The referenced code is essentially the same as yours just separated logically for easier maintenance :)