Validating User Entries

A. Vision Applications from a User’s Perspective : Using Lookup Tables and the ListChoices Operation : Validating User Entries

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You can include a Lookup table for a field on a frame. The Lookup table validates the user's entry when the user enters a value directly into a field, rather than selecting ListChoices and choosing from the selection list.

For example, assume that a user calls the AddOrders frame described above (see the first figure in this appendix). However, the user enters a value into the customer number field rather than using ListChoices to choose from the selection list.

Here is how the Lookup table functions in this case:

User Action	Vision Response
Enters a customer number	Checks the Customers table for that number If the customer number is in the table, moves the cursor to the next field. If the customer number is not in the Lookup table, displays an error message to the user.
Then either enters another customer number, or	Checks the entry again as above
Uses ListChoices with the selection list as described in the previous example	Enters the customer number on the form as in the previous example