The latest versions 7.4.0 and 7.4.1 have a new option Cancel execution by user defined time that enables you to set a specific time to terminate the execution of each SQL statement. Since you are not seeing this option, you should download the upgrade to version 7.4.1.
You will find this option on the Tuning Lab | Execution | Execution Criteria | SQL Termination page in the Options Window.
Before you execute the SQL alternatives, select only the alternatives that you want to execute. Make sure that your original SQL statement is not selected. SQL statements are “selected” if an “x” is in the box at the beginning of the row.
When you execute the SQL alternatives, use the Execute Selected option.