About return values for DataWindow events – PB Docs 2018

The way to specify a return code in a DataWindow event is different
in each of the DataWindow environments.

PowerBuilder

Use a RETURN statement as the last statement in the event script.
The datatype of the value is long.

For example, in the ItemChanged event, set the return code to 2 to
reject an empty string as a data value:

Java

Use the setReturnCode method of the event object passed to the
event. The datatype of the value is int. The setReturnCode method is
inherited from the parent EventData class.

For example, in the retrieveStart event, prevent the DataWindow from
being reset, so that the newly retrieved rows as appended to the rows
already retrieved: