Create form with Cancel Query option

Set the form level property Interaction Mode to Blocking or non-Blocking.
When set to non-Blocking, a dialog box appears that contains the following prompt:

Press cancel to end this database operation

When a long running query is executed in forms, this enables the option to interrupt the query by pressing the cancel button. However, this only works for Forms blocks which are based on standard tables or views.
It does not work for blocks based on stored procedures, where the data is returned by a ref cursor or a table of records.