Field-Level Validation Techniques in Visual Basic 6
Field-level validation (as opposed to form-level validation) has
to do with the verification of data entered into an individual field. Typically
(but not always), field-level validation is performed without regard to the contents
of other fields on the form. The appropriate times to perform field-level validation
As the user enters individual keystrokes into the field (Keystroke events
as described in previous sections).
When the user attempts to leave the field—since we presume that the
user considers the field entry to be complete (Validate event).
When the field changes for any reason (Change event).