The OnChange event for fields is hard to spot. But if you found it once you will never want to life without it. The event is quite straight forward. It gets fired every time the field content is changed and the user leaves the field. The OnChange event works for all kind of fields including rich text fields.

Most developer think that this event only works in the web with JavaScript because this is the default. But if you change "Run" to "Client" instead of "web" you can select LotusScript as the programming language.

I love this event because I no longer need to write the item value to a variable while entering the field and on exiting compare the variable with the current item value. The OnChange event will be triggered only if there was really a change.