OnValidate (Page fields) Trigger
Runs when a field loses focus after its value has been changed.
trigger OnValidate() begin ... end;
Use this trigger to validate user entries in a page field. If validation fails, then the field is marked with an error and its value is not saved.
The OnValidate trigger is also a field trigger at the table level. For more information, see OnValidate (Fields) Trigger. If both the table field and page field triggers are defined, then the OnValidate trigger on the table field is run before the OnValidate trigger on the page field.
You can use this trigger to write to the database. You cannot call the UPDATE from this trigger.