Customizing the error message – PB Docs 2018

When you define a validation rule, PowerBuilder automatically
creates the error message that displays by default when users enter
an invalid value:

You can edit the string expression to create a custom error
message.

Different syntax in the DataWindow
painter

If you are working in the DataWindow painter, you can enter a
string expression for the message, but you do not use the @ sign for
placeholders. For example, this is the default message:

A validation rule for the Salary column in the Employee table
might have the following custom error message associated with
it:

If users enter a salary less than or equal to $10,000, the
custom error message displays.