To override a default variable for an existing test,
  perform the following steps:

  1. Pull down the Maintenance menu.

  2. Choose the Modify menu item and the Test... submenu
     item.

  3. Click on the Options... button.

  Most tests use a variable's default value. For tests
  that require special handling or special variable
  values, you can override existing variables.

  You can also override a variable's default value when
  you create the test by clicking on the Options...
  button in the Create Test dialog box, then entering
  the variable and a replacement value into the Variables
  field.

  You can override a global variable for a collection
  when you create the collection by clicking on the
  Options... button in the Create Collection dialog box.