You can set the point at which
validation occurs—when the user clicks outside the widget, as the
user types, or when the user tries to submit the form.
Select a Validation Text Area widget in the Document
window.
In the Property inspector (Window > Properties),
select the Validate On option that indicates when you want validation
to occur. You can select all of the options or none of them.
Blur
Validates whenever the user clicks outside the text field.
Change
Validates as the user changes text inside the text field.